Description
The emergence of coronavirus 2019 (COVID-19) has caused an unprecedented global public health crisis. Numerous efforts have been made worldwide to prevent infection and disease. Vaccination is crucial for the control of COVID-19. Data on factors that affect neutralizing antibodies after vaccination are essential for monitoring the performance of COVID-19 vaccination programs and for the planning of public health policy decisions. Thus, six months after vaccination rollout in metropolitan France, we conducted a study to assess the immunoglobulin G (IgG) response and the presence of neutralizing antibodies against SARS-CoV-2 among primary healthcare workers (PHCW) and to identify factors associated with the detection of neutralizing antibodies.
We conducted a French national cross-sectional study among general practitioners (GPs), pediatricians, dental and pharmacy workers in primary care between May 10 and August 31, 2021. Participants recruited into the study, provided a blood sample and completed a questionnaire. Spike (S) and Nucleocapsid (N) proteins were detected and quantified using the Enzyme-linked immunosorbent assay and neutralizing antibodies with a virus neutralization test. Determinants of neutralizing antibodies detection were investigated using logistic regression analyses.
Overall, 1612 PHCW were included. The overall seroprevalences were: 94.7% (95% confidence interval [CI]: 93.6%–95.7%) for antibodies against the S protein, 23.6% (95% CI, 21.6%–25.7%) for antibodies against the N protein, and 81.3% (79.4%–83.2%) for neutralizing antibodies. Multivariate regression analyses showed that detection of neutralizing antibodies was significantly more likely in PHCW with previous SARS-CoV-2 infection than in those with no such history among the unvaccinated (adjusted odds ratio [aOR] = 16.57; 95% CI, 5.96–59.36) and those vaccinated with one vaccine dose (aOR = 41.66; 95% CI, 16.05–120.78). Among PHCW vaccinated with two vaccine doses, the detection of neutralizing antibodies was not significantly associated with previous SARS-CoV-2 infection (aOR = 1.31; 95% CI, 0.86–2.07), but was more likely in those that received their second vaccine dose within the three months prior to the beginning of the study than in those vaccinated more than three months earlier (aOR = 5.28; 95% CI, 3.51–8.23).
These results highlight that when planning booster doses and designing COVID-19 vaccine strategies, we should not only focus on the virus at the molecular level, but at human population level as well, taking into account previous infection with SARS-CoV-2 and the time since vaccination. Furthermore, these data will subsequently be used to prevent and control future epidemics.
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