It has been well established that syphilis rates have been rising both nationally and internationally. The CDC reported a 24% increase in primary and secondary syphilis rates among reproductive aged women in U.S. from 2019–2020, resulting in a 15% increase in CS rates over this time.(12) More recently, the CDC reported a 52.3% increase in primary and secondary syphilis rates among women of reproductive age from 2020–2021.(13) Our data support these findings and show that, while the majority of these cases occurred outside of the Northeast, NJ syphilis rates generally followed a similar trend to the rest of the country prior to the COVID-19 pandemic. Further, the spike in CS cases at our hospital above national and state rates in 2020 point towards factors specific to our hospital or patient population that is influencing CS transmission. These may be related to patient population that is predominantly government insured or uninsured, or other factors that may influence a city population that is low in access to health care resources.
While we cannot be definitive, the temporal association in our study, and other recent studies, suggest that the COVID-19 pandemic has only amplified the factors involved in this increase.(10) There are many reasons the pandemic could have had this effect, including the lack of access to health care leading to late maternal initiation of care, screening, and treatment that could have prevented infant transmission. This is represented well by the rate of vertical transmission, which showed a rise in 2020 after remaining between 0–50% during the pre-COVID period. This suggests that the increase observed was not due solely to increased maternal infection but also to inadequate methods of preventing vertical transmission during the pandemic. In 2021 and beyond, the vertical transmission rate fell back to pre-COVID levels, which further supports the impact of the pandemic on these rates. However, scientific literature has shown how syphilis and CS rates have been rising since well before the COVID-19 pandemic and therefore we cannot assume these rates will continue to fall as the pandemic becomes less prominent without additional specific intervention.
The rate of vertical transmission was interpreted as a measure of the adequacy of our hospital’s screening and treatment protocols. Different states require various levels of screening based on CDC recommendations. New Jersey state law currently mandates serologic screening at the first prenatal visit and in the last trimester or at delivery for all pregnant women.(14) Standard evaluation involves initial nontreponemal testing using a RPR or venereal disease research laboratory (VDRL) test, with confirmatory treponemal testing for positive screens.(15) A penicillin-based regimen appropriate for the stage of disease is recommended to be initiated > 30 days prior to delivery.(8) Diagnosis of CS in an infant is determined by quantitative nontreponemal serologic testing on infant serum and thorough physical examination.(16) Based on our data, these methods prevent vertical transmission about 50% of the time. The greatest areas of improvement identified in this study included inadequate prenatal care, late maternal initiation of treatment, and inadequate infant follow-up. This corroborates a meta-analysis from Brazil showing prenatal care and adequate maternal treatment as having the highest impact on CS development.(17) Hence, improved monitoring to reduce the risk of vertical transmission as well as reducing infectious syphilis burden in the general population would go a long way in reducing this burden.
Various social determinants of health are known to impact syphilis transmission. Numerous studies have demonstrated that women of color are more likely to give birth to infants with CS compared to their white counterparts.(5, 8) This relationship must been understood the context of systemic racism, in which women of color may not have the same access to prenatal care as women of other races, leading to poorer detection rates and later initiation of treatment. Aside from race, studies have also noted increased CS incidence among mothers who reported active substance use during pregnancy, recent incarceration, and homelessness.(5) The present study confirms that maternal substance use and homelessness can affect risk of developing CS. Interestingly, there was a larger proportion of employed women in the CS diagnosis group compared to the unemployed group or those who had unknown employment status. This association has not been reported in previous literature and the mechanism may be due to better access to healthcare in the employed patients.
There are some limitations to the present study. First, our definition of a positive CS case included both proven and possible cases. This was done because even unconfirmed cases require proper treatment and follow-up, as defined in the AAP Red Book, to prevent later development of symptoms. We aimed to evaluate the treatment and screening protocols at our hospital, which required analyzing these possible cases to ensure they were properly followed. However, this could have falsely elevated the case numbers at our hospital. Despite this, the same definition was used throughout the data collection so the rise in cases we observed was consistent within our data set. Also, we were limited to our EMR in determining adequacy of follow-up. If infants followed-up with physicians outside of our medical system, they would be coded as having inadequate follow-up per our methods. This could have falsely elevated the rate of inadequate follow-up. Additionally, per year rates may not have captured changes in case numbers at different time points during the pandemic. Future studies could benefit from analyzing rates on a month-by-month basis after the start of the pandemic, as this could give a better understanding of how rates changed during nationwide lockdowns versus as the lockdowns were lifted. Future studies could also examine patient opinions on how to better engage them in earlier prenatal care with a goal of identifying potential cases earlier and improving rates of appropriate treatment.