Vaccines for Health Care Personnel

Medical Center Occupational Health (MCOH) programs must protect health care personnel (HCP) against the occupational risk of vaccine-preventable diseases. This thematic review outlines the rationale for the use of recommended vaccines in HCP; summarizes the available evidence regarding vaccine effectiveness, administration, and assessment of immunity; and provides guidance for MCOH programs navigating challenging situations

"For at first, neither were the physicians able to cure it, through ignorance of what it was, but died fastest themselves, as being the men that most approached the sick." -Thucydides 1 F rom the Plague of Athens in 430 BC, to the Ebola epidemic of 2014, health care personnel (HCP) have toiled on the front lines of the battle against infectious disease, often placing themselves in harm's way in the service of their patients. Except for the military, no other occupation involves such pervasive, varied, and unpredictable exposure to workplace hazards, from musculoskeletal strains to workplace violence to psychological stress to chemical and biological agents. Protecting these essential workers requires comprehensive strategies. Safe and effective vaccines are the cornerstone of any Medical Center Occupational Health (MCOH) program.
CLINICAL NEED MCOH programs must estimate individuals' susceptibility to infectious diseases based largely on vaccination and/or serology records. The need to assess and document likely adult immunity from childhood vaccinations, in the absence of an outbreak or exposure, is perhaps unique to this occupational setting. Key questions for each vaccine-preventable disease (VPD) include the following: Was the correct vaccine administered appropriately? How durable is vaccine-mediated immunity? How reliable is a history of infection? How well do serologic tests correlate with immunity? Are boosters needed? How should facilities manage nonimmune HCP? Although comprehensive guidelines are periodically provided by the Advisory Committee on Immunization Practices (ACIP), most recently, in 2011, 2 recent developments in vaccine formulations and recommendations warrant an updated review.
HCP vaccination programs are needed for several reasons above and beyond protecting health care workers from occupational infection. Vaccines help employers maintain staffing by preventing postexposure furloughs and reducing HCP concerns about working during pandemics. 3 Although available evidence demonstrates that HCP are far more often victim than vector, 4-7 decreasing risk of transmission to patients and others is another important reason to protect HCP.

SCIENTIFIC OVERVIEW OF CLINICAL STUDIES
This review uses the Centers for Disease Control and Prevention (CDC) definition of HCP: "all paid and unpaid persons working in health-care settings who have the potential for exposure to patients and/or to infectious materials, including body substances, contaminated medical supplies and equipment, contaminated environmental surfaces, or contaminated air." 2 In considering the scientific evidence underpinning recommendations for HCP, we must consider vaccine efficacy (VE) for this population, when known. As the health care workforce is aging and includes people with chronic diseases, VE estimates for healthy adults below age 65 may overestimate VE in this population.

Hepatitis B Vaccine
Rationale for HCP Vaccination. Hepatitis B virus (HBV) is a highly contagious bloodborne pathogen, with a transmission risk of 10% to 30% via needlestick or other percutaneous exposure. 2 Patients with hepatitis B e antigen or high levels of HBV DNA are the most contagious, although all patients with detectable HBV surface antigen (HBsAg) are infectious. 8 Health care personnel are at occupational risk of exposure to blood or other potentially infectious materials (OPIM). 9 Since 1989, the CDC has recommended HBV vaccination for all HCP. Following implementation of the Occupational Safety and Health Administration's Bloodborne Pathogen Standard in 1991, requiring health care employers to provide vaccination to all potentially exposed HCP, 10 vaccination rates increased dramatically. 11 Occupationally acquired HBV, once common, has become rare. 12 Nevertheless, vaccine coverage remains suboptimal; approximately 25% of US HCP with direct patient contact report never completing a 3-dose series. 13 Universal childhood vaccination is now the cornerstone of US HBV-elimination strategy. 14 HBV vaccine is highly effective in infants, achieving serologic conversion rates above 95%. The vaccine is less immunogenic in adults. 15 Among HCP aged 18 to 40, the 3-dose series of recombinant HBV vaccine is 86% to 90% effective, but seroconversion rates are lower in HCP older than 40, especially those with chronic diseases. 16 Vaccine Administration, Formulations, and Boosters. Correct vaccine administration and timing are crucial. Standard recombinant HBV vaccine is administered at 0, 4, and 24 weeks as an intramuscular (IM) injection. Accelerated vaccination schedules are not more effective, and immunogenicity is hampered by delays in the second dose or administration into the gluteus muscle. 17 A newly approved hepatitis B vaccine, HBsAg-1018, uses a toll-like receptor 9 agonist adjuvant. This vaccine is given in a 2-dose series, administered at 0 and 4 weeks. This formulation produces better seroprotection than the 3-dose vaccine, significantly shortening the vaccination series without sacrificing safety. [18][19][20][21] Despite higher cost per dose, the convenience and improved immunogenicity of the 2-dose series makes it a cost-effective option for MCOH programs. 22 HBV surface antibody (HBsAb) levels wane over time in a large percentage of people vaccinated over 10 years previously; anamnestic responses to vaccine boosters in this population indicate that once established, immune memory is preserved. [23][24][25] Routine boosters are not necessary.
Serologic Evidence of Immunity. Following the final vaccine dose, HCP should have immunity assessed via serology with IgG for HBsAb. Those lacking seroprotective HBsAb following the initial series should undergo a second series, with another HBsAb 4 weeks after completion. Consideration should be given to using the 2-dose adjuvanted HBsAg-1018 vaccine in adults because of its higher immunogenicity. Following 2 complete series, more than 90% of adults will develop immunity, although there is an inverse association with age. 2 HCP who fail to develop protective levels of HBsAb after 2 complete series of vaccine are considered "nonresponders." Despite lack of a robust humoral immune response, most nonresponders seem to develop HBsAgspecific memory B cells. 26 Three doses of intradermal recombinant vaccine stimulates seroconversion in a high proportion of nonresponders and is reasonable to offer to this population. [27][28][29] Nonresponders and previously unvaccinated nonimmune HCP exposed to blood or OPIM known or suspected to be contagious for HBV should receive postexposure immunoprophylaxis with hepatitis B immune globulin, along with HBV vaccine if incompletely vaccinated, per CDC guidelines. 8 The phenomenon of waning HBsAb levels presents a quandary for evaluating HCP vaccinated in childhood, as most will not have previous documentation of seroconversion. Although more than 95% of individuals vaccinated in infancy are likely to have durable immunity, 60% to 85% of those tested more than 10 years after vaccination will have an HBsAb below 10 IU/mL. [23][24][25] One challenge dose of vaccine will result in an anamnestic response in the vast majority of these adults. 24,25 Health care facilities have 2 options for managing previously vaccinated HCP without documentation of postvaccine serology: preexposure serology for all at-risk employees or immediate postexposure HBsAb for all HCP who report occupational exposures to blood or OPIM. Cost-effectiveness comparisons suggest that pre-exposure assessment is more expensive but prevents more occupational infections. The cost per quality-adjusted life year is high for both strategies and differs with length of employment, with the pre-exposure strategy becoming more cost effective after 3 years. 30 Measles, Mumps, and Rubella (MMR) Vaccine Rationale for Vaccination of HCP. Although measles was declared eradicated from the United States in 2000, outbreaks continue to occur because of continued global prevalence, international travel, and lack of uniformly high US vaccination rates. 31 Because people with measles often need medical care, HCP have a relative risk between 2 and 19 of contracting measles compared with the general population. 4 Recently, outbreaks of mumps in communities, colleges, and hospitals have reinforced the need to maintain HCP immunity. 32 Although endemic transmission of rubella was eliminated in the United States in 2004, imported cases of rubella continue to occur. A recent occupational exposure to a nonimmune health care worker emphasizes the ongoing risk. 33 Vaccine Administration, Formulations, and Boosters. Vaccines against measles, mumps, and rubella were first licensed in 1963, 1967, and 1969, respectively. Trivalent MMR vaccine was licensed in 1971 and has supplanted singleantigen vaccines. ACIP recommended universal childhood vaccination with MMR, which quickly became a standard US school entry requirement. 34 The CDC has recommended HCP MMR vaccination since 1987, evolving to current recommendations of 2 doses of measles and mumps and 1 of rubella for HCP who lack evidence of immunity. 2 Evidence of immunity includes appropriately timed immunization (2 doses after age 12 months, separated by at least 28 days, for measles and mumps; 1 dose after age 12 months for rubella), laboratory evidence of immunity or disease, or birth before 1957. In an outbreak situation, these older HCP should also be vaccinated if they lack laboratory evidence of immunity. Given the logistic challenges and resource constraints facing MCOH programs during outbreaks, facilities may choose to apply the same requirements for all HCP, regardless of age.
Serologic Evidence of Immunity. Case reports of vaccinated HCP contracting measles raise the question of whether vaccination is adequate evidence of immunity. [35][36][37] Unfortunately, available serologic assays are inadequate to assess immune status fully. Individuals with positive IgG titers have become infected with measles and mumps. 37,38 Vaccine-induced antibody may be effective against vaccine-strain antigens and yet lack efficacy against wild-type virus. 38 Negative serology can underestimate immunity because it cannot detect crucial vaccinemediated cellular immune responses. 39,40 Among commercially available test methodologies to detect IgG, enzyme immunoassay (EIA) is the most sensitive. 41,42 Although IgG provides reasonable, if imperfect, evidence of immunity, postvaccination serologic surveillance is not recommended.
MCOH programs must often document immunity in newly hired HCP without vaccination records. Cost effectiveness of vaccination vs prevaccination serologic screening will vary with population seroprevalence and costs of laboratory testing and vaccine. Institutions can reasonably select either option, or a combination approach, depending on operational constraints and HCP preferences. 43 Special Considerations. MMR vaccination must be deferred in (nonimmune) pregnant VACCINES FOR HEALTH CARE PERSONNEL and immune-compromised HCP for whom live virus vaccines are contraindicated. Like their patients, these HCP depend on scrupulous attention to isolation and personal protective equipment (PPE) protocols for potentially contagious patients. We strongly advocate implementing precautions for patients whose differential diagnosis includes measles, rubella, or varicella until these diseases are ruled out.
Although MMR contains attenuated virus, no clinically important shedding occurs postvaccination, and there is no need to remove HCP from patient care environments after vaccination. Approximately 5% of vaccine recipients experience a transient postvaccination rash, which is not contagious.

Varicella Vaccine
Rationale for Vaccination of HCP. Occupational exposure to varicella is a serious ongoing hazard to HCP and patients, particularly those with immune compromise. [44][45][46] Airborne transmission occurs with primary chickenpox and disseminated zoster (which may present atypically in immune-compromised individuals), but case reports have described isolated incidents of apparent airborne transmission from single-dermatome shingles. 45,47 Because transmission can occur before onset of rash, susceptible HCP should be removed from the workplace during the incubation period, days 8 to 21 postexposure. 2 Exposure to varicella in health care facilities is common, expensive, and disruptive. High infectivity and potential staffing impact make establishing HCP immunity an MCOH priority.
Vaccine Administration, Formulations, and Boosters. When varicella vaccine was introduced in 1995, HCP vaccination recommendations immediately followed. 48 This live virus vaccine, administered as a 2-dose series, is 95% effective in children and approximately 80% effective in adults. 48 Vaccine-mediated immunity is less robust than natural immunity and may decrease after 10 to 20 years. 49 Serologic Evidence of Immunity. As with MMR, commercially available EIAs are somewhat insensitive to varicella vaccineinduced antibodies. 50 Thus, although vaccine is an important tool to protect HCP, increasing childhood and adult vaccination rates complicate serologic interpretation. Although approximately 80% of adults seroconvert following vaccination, 30% may lose serologic evidence of immunity over time. 51 However, negative titers by available EIAs may underestimate clinical immunity. 52 Vaccinated adults develop less disease and less severe disease than unvaccinated controls, likely reflecting cell-mediated immunity and humoral responses not easily measured outside research laboratories. 51 In one study, 70% of vaccinated exposed HCP with negative varicella (VZ) IgG titers by EIA had evidence of immunity by the laborintensive fluorescent-antibody-to-membraneantigen assay. 53 Conversely, vaccine-induced seroconversion doesn't guarantee immunity. Even with a positive VZ IgG by EIA, HCP can have lowavidity antibody and remain susceptible, 52 possibly explaining rare occurrences of primary chickenpox in HCP with positive VZ IgG. 47 Given the relatively recent introduction of vaccine and high rates of childhood infection, especially among older HCP, much study has focused on the utility of chickenpox disease history. Seroprevalence studies indicate the positive predictive value of history to predict seropositivity is above 95%, whereas the negative predictive value of a negative or uncertain history is quite low. [54][55][56] However, as younger HCP enter the workforce, seroprevalence in unvaccinated adults will likely decrease.
Multiple cost-effectiveness studies have evaluated strategies to confirm varicella immunity, usually concluding that serologic testing only for HCP without a clear history of chickenpox infection is most cost effective. 57,58 Although a reasonable approach in resourcelimited settings, this strategy prevents fewer cases than serologic screening for all unvaccinated HCP. Screening all unvaccinated HCP is cost effective when the impact of patient exposures to infected HCP is considered. 59 Furthermore, cost-effectiveness studies overlook real-life experience in MCOH programs, in which many HCP provide previous records. US HCP often have records of vaccination or serologies from previous schools or jobs, lowering employers' costs and making serologic testing for those without documented immunity more feasible. Cost-effectiveness models are also sensitive to susceptible HCP compliance with vaccination, generally assuming a 30% declination rate. However, this depends on facility policy; requiring vaccination in the absence of contraindications would further improve cost effectiveness.
Given the potential impact to coworkers, patients, and operations from any HCP with chickenpox, the ACIP defines evidence of varicella immunity as documentation of 2 doses of vaccine, positive serology, or laboratory diagnosis of disease, not clinical history of disease. 2 Postvaccination serology is not indicated; if performed anyway, and found to be negative, there is no recommendation for a third vaccine.
Special Considerations. Varicella vaccine is a live attenuated vaccine, contraindicated in pregnancy and immune compromise. All HCP, regardless of vaccination or presumptive immunity, should use appropriate infection-control practices and PPE when caring for patients with suspected varicella. Unvaccinated staff without evidence of immunity should not be assigned to potentially contagious patients. Given concerns about relatively increased susceptibility in vaccinated vs previously infected HCP, postexposure management differs slightly for these groups. Whereas exposed HCP with natural immunity require no intervention, and unvaccinated nonimmune HCP require exclusion from the workplace during the incubation period, vaccinated HCP may continue to work after exposure with monitoring and should be evaluated and removed from work if they develop fever or rash illness during the incubation period.
Mild varicella-like rash may occur following vaccination in up to 5% of HCP; vaccine-strain varicella can be isolated from these vesicles. These HCP are not contagious via the respiratory route, so they need not be removed from the workplace entirely, but they should not have direct contact with susceptible patients at risk for varicella complications (eg, pregnant or immune compromised) until the lesions have dried or crusted.

Pertussis Vaccine
Rationale for Vaccination of HCP. Pertussis is an important cause of morbidity and mortality in children, particularly infants too young to be vaccinated. Nosocomial transmission to infants occurs in hospitals, 60 and HCP, especially those caring for children, have occupational risk of contracting pertussis. Although the disease is generally much milder in adults, HCP have experienced serious illness. 61 Pertussis in adults is common, transmissible, frequently subclinical, and often unreported. 62,63 Pertussis is spread through respiratory droplets, and health care-associated transmission can occur between HCP and coworkers as well as between patients and HCP. The experience of large hospital pertussis outbreaks in which no patients were infectedddespite receiving care from infected HCPddemonstrate the effectiveness of droplet precautions. 6,7 Hospital outbreaks are expensive, nonetheless. 6,64 Contact tracing, notification, education, and offer of postexposure prophylaxis are necessary for exposed HCP and patients. Although several outbreak reports have noted that the costs of outbreak management exceed the costs of vaccinating all HCP in a facility, there is, unfortunately, not a direct trade-off in costs. Few exposures are preventable, 64 and HCP vaccination does not fundamentally change exposure management. Because of imperfect and waning vaccineinduced immunity, vaccinated HCP should be offered postexposure prophylaxis, 65 and symptomatic HCP should be furloughed regardless of vaccine status. HCP vaccination may reduce the number and costs of outbreaks modestly in situations when the index case is a health care worker. Costeffectiveness models suggest that HCP pertussis vaccination programs are cost saving in facilities that experience at least 1 pertussis outbreak per decade 66 or when the risk of HCP-introduced pertussis exceeds 0.3% per month and the Tdap vaccination rate exceeds 25%. 67 Vaccination rates among HCP vary widely and are likely still in flux, as the vaccine was introduced relatively recently. Approximately one third of US hospitals had pertussis vaccination policies by 2011, although target population and specific requirements varied widely. 68 Surveys suggest US HCP vaccination rates have risen steeply from 27% in 2011 to 47% by 2014. [69][70][71] Voluntary vaccination programs have achieved variable results, with some reporting over 90% vaccination. 72 Some US hospitals have instituted Tdap requirements, with predictably high vaccination rates. 73,74 Despite decades of routine childhood immunization, pertussis remains endemic worldwide. Disease prevalence in adults is increasing. Although enhanced awareness and improved diagnostics may partially account for the increase in reported cases, the most important driver for this trend is likely waning vaccine-induced immunity. Childhood whole-cell pertussis vaccines have largely been supplanted by acellular vaccines, although vaccine types and schedules vary markedly across the globe. The shift to acellular childhood vaccine may decrease the durability of immunity. Among acellular vaccines, there is variability in the number and concentration of pertussis antigens and adjuvants, making direct comparisons difficult. Pertussis vaccines contain different combinations and concentrations of detoxified pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), and fimbriae serotypes 2 and 3 (FIM2 and FIM3). There is no consensus on ideal antigen composition.
Vaccine Administration, Formulations, and Boosters. Adult pertussis vaccine is combined with tetanus and diphtheria vaccine in Tdap. Two US manufacturers produce Tdap: GlaxoSmithKline (Boostrix) and Sanofi-Pasteur (Adacel). Boostrix contains 8 mg each of PT and FHA antigens and 2.5 mg of PRN, while Adacel contains 2.5 mg of PT, 5 mg of FHA, 3 mg of PRN, and 5 mg of FIM2 and FIM3. In 1 retrospective cohort study, adolescents who received Boostrix demonstrated higher antibody levels and a lower rate of pertussis infection than those receiving Adacel; however, antibody levels fell precipitously over 5 years in both groups. The World Health Organization and CDC currently recommend only 1 adolescent or adult dose of Tdap, followed by regular tetanus/diphtheria boosters at 10-year intervals, except for additional Tdap boosters in every pregnancy for maternal antibody protection of newborns. Additional periodic adult pertussis boosters have not been recommended, but some investigators have suggested that this may be useful, 75 and the safety and short-term immunogenicity of second Tdap boosters have been established. 76 Serologic Evidence of Immunity. There is no straightforward serologic correlate of protection against pertussis. IgG against PT is the most commonly used indicator, but it is the fastest-waning vaccine-induced antibody, and its absence is often compensated for by cell-mediated immunity. Studies of pertussis seroprevalence and vaccine immunogenicity differ in the antibodies used to define immunity and the cutoff values used, making both comparisons difficult.
Special Considerations. Although only 1 pertussis vaccine is recommended for adults, booster doses are recommended with each pregnancy. For maximal newborn protection, vaccine should be administered at 27 to 36 weeks' gestation. Newly hired HCP in earlier pregnancy stages should be appropriately counseled. For employers requiring pertussis vaccine, it is reasonable to defer vaccination until the optimal stage of pregnancy.

Influenza Vaccine
Rationale for HCP Vaccination. A century ago, the 1918 influenza epidemic raged around the world, with high illness and mortality rates among young adults including HCP. Death rates were higher for HCP tending the sick in the United States than those working overseas in military settings. 77 Influenza in Minnesota HCP drastically affected clinical care across the state, 78 mirroring the devastation in other states.
Influenza remains an annual occupational hazard for HCP with concerns for infection, transmission, and absenteeism. Vaccination must be an integral part of comprehensive influenza-prevention programs, although it is less effective than other HCP vaccines. In a metanalysis of VE in adults aged 18 to 65, excluding seasons in which the vaccine did not match circulating strains, the pooled efficacy of trivalent inactivated vaccine was 59%. 79 Despite its modest VE, the benefits of vaccination to HCP are clear, with reductions in both illness and absenteeism. 80 Overall evidence supportsdand the CDC recommendsdaiming for universal annual immunization of HCP. 81 Naturally, there is interest in whether HCP vaccination benefits their patients. HCP may be more likely than other professions to work when ill, posing a risk for transmission of influenza and other respiratory illnesses to medically vulnerable patients. Infection-control practices, such as handwashing, likely mitigate this risk. Studies addressing the impact on patients from HCP immunization are strongest in long-term care (LTC) settings, where patients are both most vulnerable to influenza complications and most likely to remain in situ during the incubation period. Ironically, HCP vaccination rates are lowest in this setting. 82 Several cluster randomized trials found associations between all-cause mortality and ILI among LTC residents and voluntary HCP vaccination programs achieving modest rates of vaccination. [83][84][85] The lack of an effect on influenza infection in residents, the presence of bundled educational interventions, and lack of blinding in these studies necessitates a cautious interpretation, especially if extrapolating these findings to different interventions or clinical settings. Comprehensive influenza-control programs, including increased HCP vaccination, have been associated with a decline in nosocomial influenza among patients. 86,87 Systematic reviews have not found strong evidence of a protective effect to patients from HCP influenza vaccine, [88][89][90] but there may be an interactive effect between vaccination of patients and HCP. Studies in LTC have found an association between influenza outbreaks, HCP vaccination rates, and resident vaccination rates. 91,92 Vaccine Administrations, Formulations, and Boosters. Influenza vaccines are generally inactivated IM products designed to induce immune protection against the 3 or 4 strains judged most likely to circulate in a coming influenza season. 81 As the majority of vaccines are manufactured in eggs with production cycles of up to 6 months, the strains must be identified well before influenza begins circulating in the United States. Genetic drift and shift during that period can drastically alter vaccine effectiveness year to year. Recently, cell-based and recombinant vaccines have shown promise in terms of shorter production cycles and better immune protection.
Among inactivated IM influenza vaccine products, adjuvanted and high-dose vaccines may confer additional protection for adults older than age 65. 81 There is some evidence that recombinant vaccine may be more effective in adults older than age 50. 93 In addition to inactivated influenza vaccines, a live attenuated product has been intermittently ACIP-approved for healthy nonpregnant adults below age 50, including HCP. 94 This product has obvious advantages for needle-averse staff; however, there are ongoing concerns about its effectiveness compared with injectible products. Intradermal vaccines have also been ACIP approved during some flu seasons. The spectrum of influenza vaccine products increases every year, and MCOH professionals should consult the most recent recommendations before making purchase decisions.
Special Considerations. Overall, annual influenza immunization rates for US HCP have risen steadily, but only inpatient hospital HCP have met the Healthy People 2020 goal of 90%. 82 Influenza immunization for HCP differs from other immunizations for this population because it must be an annual program. Specific challenges include reaching In outbreak or exposure situation, birth before 1957 is not adequate evidence of immunity.

Rubella
All HCP One rubella/MMR vaccine, given after 12 months of age, or Positive rubella IgG, or Laboratory evidence of infection, or Birth prior to 1957.
Do not perform postvaccination rubella IgG. If performed and results are negative, additional doses of vaccine are not indicated.
In outbreak or exposure situation, birth before 1957 is not adequate evidence of immunity.

Varicella
All HCP Two varicella vaccines, given at least 28 days apart and after 12 months of age, or Positive varicella IgG, or Laboratory evidence of infection.
Do not perform post vaccination varicella IgG.
If performed and results are negative, additional doses of vaccine are not indicated.
ACIP guidelines include verification of disease history or clinical diagnosis from any health care provider as acceptable evidence of immunity. However, mild or atypical disease may be incorrectly attributed to varicella, and such clinical details are rarely available to MCOH programs. In our opinion, obtaining a varicella IgG in these situations is reasonable.

Continued on next page
HCP on all shifts, purchasing and deploying vaccine and related supplies, and obtaining adequate staffing to vaccinate during the recommended time frame each year. Factors associated with successful MCOH influenza immunization programs include free and convenient vaccine on all shifts and in all locations, well-advertised special events, adequate staffing, and employee education. 95,96 Employer requirements for annual HCP immunization can dramatically increase annual participation. 74,96,97 Current research efforts to develop influenza vaccines with shorter manufacturing cycles, better effectiveness, more conserved antigenic targets, and durable immunity are promising. The "holy grail" of a universal influenza vaccine would greatly benefit HCP as well as their patients and communities.

Vaccines for Targeted Subpopulations
Although most HCP are exposed to patients or the patient care environment, others may have occupational exposure to more unusual pathogens. Where safe and effective vaccines exist, they should be offered to protect workers from those hazards.
Microbiologists who handle specimens potentially containing meningococcus should be vaccinated with both the ACWY and serogroup B vaccines. Both are inactivated vaccines; for ongoing occupational exposure, boosters every 5 years are recommended. 98 Similarly, microbiologists who manipulate samples likely to contain salmonella typhi should be offered typhoid immunization, available as either a live oral vaccine, which is boosted every 5 years, or as an inactivated IM injection every 2 years. 99 Consultation with laboratory medical directors and infection-prevention personnel is advisable to identify exposure risks for each laboratory.
Recommended vaccines for HCP, with the correlates of immunity and related management strategies reviewed above are summarized in Tables 1 and 2. Vaccinations for research laboratory personnel are complex and outside the scope of this review. MCOH programs serving biomedical research laboratories should work closely with their institutional biosafety officers and research animal MCOH programs need appropriate resources and authority to respond to evolving HCP vaccine recommendations. For instance, ACIP has recently recommended third doses of MMR during community and campus mumps outbreaks. 100 Compliance software may need to adapt to a third MMR requirement for targeted HCP groups in outbreak situations. Compliance software must accommodate new vaccine products and combinations, vaccine schedule changes (eg, 2-dose HBV vaccine), and institutional policy changes (eg, Tdap requirements for pediatric HCP). Investment in robust and highly flexible MCOH compliance tracking software is vital. Operational requirements for HCP vaccination programs are summarized in Table 3.
Management of nonimmune HCP with vaccine contraindications or refusals poses another challenge to MCOH programs. Although it is preferable to keep known susceptible HCP away from patients with known or suspected VPDs, vaccination never obviates the need for PPE and other precautions. Absent identified threats, such as suspected cases or outbreaks, facilities must make risk-based assessments, considering the community prevalence of the VPD and the HCP's jobs. In most cases, the risk of occupational infection is manageable, and unvaccinated HCP can work with appropriate restrictions. Patient safety must also be considered. Except for seasonal influenza, the risk of nonoccupational VPDs in the United States is low, and asymptomatic HCP do not pose a significant risk to patients absent from known exposure. Even for influenza, routine use of masks to prevent transmission of disease from asymptomatic HCP (vaccinated or not) is not supported by evidence.
CDC recommendations to check HBsAg, HBV core, and surface antibodies only in HCP who have immigrated to the United States from countries with endemic HBV present Research assessing the utility of boosters in at-risk occupational groups is needed. Varicella zoster (shingles) vaccine is now recommended for adults older than age 50 without prevaccination screening for VZ IgG. 101 However, primary varicella vaccination is still recommended for HCP without evidence of immunity, including those above age 50. Vaccination with 2 doses of shingles vaccine has not been acknowledged as evidence of varicella immunity, so MCOH programs face an awkward recommendation for testing HCP above age 50 for VZ IgG and, if negative, providing low-dose primary varicella vaccine. HCP in this situation need clear guidance for whether and when to obtain shingles vaccines. Research is needed to determine whether 2 doses of shingles vaccine can suffice as evidence of immunity in HCP older than 50 years of age.
Human papillomavirus and other VPDs are found in bioaerosols to which surgical staff may be exposed. 102 Engineering controls to evacuate surgical smoke and respiratory protection programs can mitigate this risk, but the role of HPV vaccine remains unclear in this population. HPV vaccine is not recommended for adults above the age of 26, 103 but the vaccine is newly licensed up to age 45, 104 potentially facilitating its use in occupationally exposed HCP. However, the vaccine's effectiveness for protection against HPV respiratory exposure is unknown.

CONCLUSIONS
MCOH professionals manage complex vaccination programs, not only providing vaccines ☐ Trained occupational nurses who understand principles of vaccination, immunity assessment, employee rights and requirements, employer obligations, OSHA regulations, and institutional policy ☐ Medical direction by physician knowledgeable about vaccine-preventable diseases and the regulatory landscape of occupational medicine ☐ Institutional policy that clearly defines required vaccines/tests, optional vaccines, exemption procedures, and consequences of policy noncompliance ☐ Onboarding process that includes obtaining complete vaccination records when possible ☐ Privacy policy that communicates compliance status to supervisor without disclosing HCP medical information ☐ Procedure for evaluating vaccine exemption requests ☐ Written protocols for screening records and providing needed services ☐ Electronic tracking system for vaccine and serology records with the following: ☐ Daily or real-time update of personnel and jobs from HR system ☐ Routine reports to monitor compliance/completion of onboard screening ☐ Rapid retrieval of data for exposure management ☐ Quality assurance procedures in place to maintain data integrity ☐ Flexibility to adapt to changing immunization formulations, schedules, and requirements ☐ Process for ensuring vaccination/immunity for nonpaid or nonemployed personnel (licensed independent practitioners, students, contractors, volunteers, and visiting staff) that mirrors requirements for employed HCP ☐ HCP education on infection control practices and reporting of exposures and symptoms HCP ¼ health care personnel; HR ¼ human resources; OSHA ¼ Occupational Safety and Health Administration.

VACCINES FOR HEALTH CARE PERSONNEL
Mayo Clin Proc. n October 2019;94(10):2127-2141 n https://doi.org/10.1016/j.mayocp.2019.01.035 www.mayoclinicproceedings.org but assessing adult immunity from childhood records and serologies based on evolving evidence. These programs are crucial to protect HCP, their families, patients, and employers. Well-trained staff, adequate resources, and robust technology are necessary to deliver evidence-based effective programs. Coordination with a wide variety of stakeholders is needed. Effective HCP vaccination programs follow best practices in immunization and confidentiality, while simultaneously and continuously interfacing with medicalcenter human resource officers, infectioncontrol staff, and regulatory demands. Doing so requires a range of training, policies, and protocols, many of which are unique to the MCOH setting. More research is needed to resolve common but challenging questions about assessing and maintaining immunity in this adult population with ongoing risk of exposure to VPDs.