Long-term immunity after HBV vaccine: shall we consider a change? A 20-year-follow-up study

Abstract Introduction Although vaccines against HBV have been available since the 1980s, the long-term immunity is still debated. When assessing immune persistence, a number of clearly defined variables must be taken into account. Often the expression ‘infant vaccination’ means the administration within the first year of life at any age, but a difference of a few months may imply a different antibody persistence over the years. This study assessed the anti-HBs titre 20 years after the primary vaccination course and estimated the effect of age at 1st dose and time interval between doses on long-term protection. Methods Data on age, sex and date of administration were collected. Inclusion criteria: born to negative mother, 3-dose schedule, no previous HBV infection, age at enrolment 18-24 years; age at 1st dose 2-12 months. Titres ≥10IU/l were considered protective. A logistic regression was performed, adjusting for sex, follow-up time and date of 1st dose and analysis. Results We included 5,485 participants (64% female). The mean anti-HBsAg increased from 46, 52, 85 to 193IU/l when the 1st dose was administered in the I, II, III or IV trimester of life, respectively. Similarly, the proportion of individuals with titre <10IU/l decreased from 51 to 18% between the two extreme quarters. The risk of a titre <10IU/l decreased with age at the 1st dose (AOR: 0.84; 95%CI: 0.78-0.91 per one-month increase) and time between the 2nd and 3rd doses (AOR: 0.89; 95%CI:0.85-0.94). Conclusions The mere presence of a titre <10IU/l does not equate lack of protection. However, antibody levels are very different depending on the actual age of vaccination. One-month delay within the first year is associated with a -18% chance of a titre <10IU/l 20 years later. Although this information needs to be combined with local epidemiology and surveillance to obtain an informed risk-benefit balance, the implications from a public health and economic perspective may be diverse and worth considering. Key messages • Still within the first year of life, a delay in the administration of the 1st dose of HBV vaccine and a longer time between the 2nd and 3rd dose imply a higher antibody persistence even 20 years later. • Considering the local circulation of HBV and surveillance, this result could be taken into account to obtain an informed risk-benefit balance.


Background:
Social distancing policies to reduce transmission of covid-19 also reduced children's exposures to endemic respiratory viruses. We aimed to examine the impact of the covid-19 pandemic on lower respiratory tract infections in under 5s presenting to primary care in England.

Methods:
Longitudinal trends analysis using electronic health records from a nationally representative primary care database. Our target population was children aged <5 years registered with a primary care practice from January 2015 to March 2021. Our main outcome was total weekly contacts with primary care for a lower respiratory tract infection (LRTI). We defined three pandemic phases from March 2020 -March 2021: i) first national lockdown (late March to early June 2020), ii) childcare settings reopened and second national lockdown with schools open (mid-June to mid-December 2020) and iii) third national lockdown with schools closed (late December 2020 to end of March 2021). We compared outcomes during each of the three phases with corresponding calendar weeks during pre-pandemic years 2015 to 2019.

Results:
Our study population included 843 020 children <5 years who had 1 076 181 contacts with primary care for LRTIs. During the first phase (first lockdown) there were falls of 79.3% (95% CI: 73.6 to 84.5) from an average of 28 547 primary care contacts for LRTI in 2015 -2019 to 5915 in 2020; there was a 78.9% (95% CI: 73.7 to 83.9) fall in phase two (childcare settings reopened and second lockdown) from 107 873 to 22 792 contacts; and a 77.7% (95% CI: 73.5 to 81.4) fall in phase three (third lockdown) from 57 200 to 12 764 contacts.

Conclusions:
Children under 5 in England had fewer contacts with primary care for LRTIs during the covid-19 pandemic. This change likely reflects lower prevalence of respiratory illness due to fewer social contacts. This may impact on future health service use as these children have had less exposure, and therefore may have less immunity, to respiratory diseases.

Key messages:
Children under 5 had fewer contacts with primary care for lower respiratory tract infections during the covid-19 pandemic in England likely due to the restrictions in place to reduce social contacts. The falls in lower respiratory tract infections during the covid-19 pandemic in under 5s may mean they have less immunity to respiratory viruses which may impact upon their future health service use. 1st dose (AOR: 0.84; 95%CI: 0.78-0.91 per one-month increase) and time between the 2nd and 3rd doses (AOR: 0.89; 95%CI:0.85-0.94).

Conclusions:
The mere presence of a titre <10IU/l does not equate lack of protection. However, antibody levels are very different depending on the actual age of vaccination. One-month delay within the first year is associated with a -18% chance of a titre <10IU/l 20 years later. Although this information needs to be combined with local epidemiology and surveillance to obtain an informed risk-benefit balance, the implications from a public health and economic perspective may be diverse and worth considering. Key messages: Still within the first year of life, a delay in the administration of the 1st dose of HBV vaccine and a longer time between the 2nd and 3rd dose imply a higher antibody persistence even 20 years later. Considering the local circulation of HBV and surveillance, this result could be taken into account to obtain an informed risk-benefit balance.

Background:
Higher family affluence is associated with healthier behaviours in adolescents, but the strength of this association varies across countries. Differences in social mobility at the country-level, i.e. the extent to which adolescents develop a different socioeconomic status (SES) than their parents, may partially explain why the association between family affluence and adolescent health behaviours is stronger in some countries than in others.

Methods:
Using data from adolescents aged 11-15 years from 32 different countries, participating in the 2017/2018 wave of the Health Behaviour in School-aged Children (HBSC) study (N = 185,086), we employed multilevel regression models with cross-level interactions to examine whether country-level social mobility moderates the association between family affluence and adolescent health behaviours (i.e. moderate-tovigorous physical activity, vigorous physical activity, healthy foods consumed, unhealthy foods consumed, having breakfast regularly, weekly smoking).

Results:
Higher family affluence was more strongly associated with higher levels of physical activity in countries characterized by high levels of social mobility (cross-level interaction linear regression coefficient 0.34; 95% CI 0.08 to 0.60; p = 0.009 for moderate-to-vigorous physical activity, and 0.31; 0.11 to 0.50; p = 0.002 for vigorous physical activity). No cross-level interactions were found for any of the other health behaviours.

Conclusions:
Our findings suggest that differences in social mobility at the country-level may contribute to cross-national variations in socioeconomic inequalities in adolescent physical activity. Further research can shed light on the mechanisms linking country-level social mobility to inequalities in adolescent physical activity to identify targets for policy and interventions.
Key messages: This is one of the first studies to investigate country-level social mobility in relation to health equity. Inequalities in adolescent physical activity were steeper in socially mobile countries. Stronger efforts to engage adolescents from low-affluent families in physical activity may be necessary in countries characterized by high levels of social mobility.

Background:
Cross-sectional studies have suggested a relationship between social media use and depression and anxiety in young people. We examined the longitudinal relationship between social media use and young people's mental health and the role of self-esteem and social connectedness as potential mediators.

Methods:
The sample comprised 3,228 young people from the UK Longitudinal Household Study (waves 1-10). Mental health at age 14 or 15 was measured by the SDQ Total Difficulties score. The number of hours spent on social media was measured at age 12 or 13. Self-esteem at age 13 or 14 was measured via eight questions and social connectedness was measured by two questions. Multilevel linear regression models explored whether social media use at age 12 or 13 predicted mental health at age 14 or 15. Path analysis with structural equation modelling investigated the mediation pathways.

Results:
In unadjusted analysis, for those who spent 7 or more hours on social media vs none, their mental health problems trended upwards by 3.87 (95% CI, 0.71-7.03) but this relationship was