Abstract
Background: BNT162b2 was shown to be 92% effective in preventing COVID-19. Prioritizing vaccine rollout, and achievement of herd immunity depend on SARS-CoV-2 transmission reduction. The vaccine's effect on infectivity is thus a critical priority. Methods: Among all 9650 HCW of a large tertiary medical center in Israel, we calculated the prevalence of positive SARS-CoV-2 qRT-PCR cases with asymptomatic presentation, tested following known or presumed exposure and the infectious subset (N-gene-Ct-value<30) of these. Additionally, infection incidence rates were calculated for symptomatic cases and infectious (Ct<30) cases. Vaccine effectiveness within three months of vaccine rollout was measured as one minus the relative risk or rate ratio, respectively. To further assess infectiousness, we compared the mean Ct-value and the proportion of infections with a positive SARS-CoV-2 antigen test of vaccinated vs. unvaccinated. The correlation between IgG levels within the week before detection and Ct level was assessed. Findings: Reduced prevalence among fully vaccinated HCW was observed for (i) infections detected due to exposure, with asymptomatic presentation (VE(i)=65.1%, 95%CI 45-79%), (ii) the presumed infectious (Ct<30) subset of these (VE(ii)=69.6%, 95%CI 43-84%) (iii) never-symptomatic infections (VE(iii)=72.3%, 95%CI 48-86%), and (iv) the presumed infectious (Ct<30) subset (VE(iv)=83.0%, 95%CI 51-94%). Incidence of (v) symptomatic and (vi) symptomatic-infectious cases was significantly lower among fully vaccinated vs. unvaccinated individuals (VE(v)= 89.7%, 95%CI 84-94%, VE(vi)=88.1%, 95%CI 80-95%). The mean Ct-value was significantly higher in vaccinated vs. unvaccinated (27.3±1.2 vs. 22.2±1.0, p<0.001) and the proportion of positive SARS-CoV-2 antigen tests was also significantly lower among vaccinated vs. unvaccinated PCR-positive HCW (80% vs. 31%, p<0.001). Lower infectivity was correlated with higher IgG concentrations (R=0.36, p=0.01). Interpretation: These results suggest that BNT162b2 is moderately to highly effective in reducing infectivity, via preventing infection and through reducing viral shedding.
| Original language | English |
|---|---|
| Article number | 100150 |
| Journal | The Lancet Regional Health - Europe |
| Volume | 7 |
| DOIs | |
| State | Published - Aug 2021 |
| Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2021 The Author(s)
Funding
The following financial relationships have been disclosed by the authors, all are not directly related to the submitted work: GRY received grants for work on pneumococcal disease from Pfizer and for work on volatile organic compounds and COVID-19 form Nanosens. ML support for the present manuscript was funded by NIH/NCI and the Morris-Singer fund. He received non-related to this work grants from Pfizer, US-CDC, open philantropy project, waking up foundation, NIH/NIGMS, NIH/NIAID, UK National Institute for Health research, consulting fees from Merck and the University of Virginia, Miller Center. Honoraria for lectures from Sanofi Pasteur and Bristol Myers Squibb. Participated on a Data Safety monitoring Board/Advisory board of Fred Hutch Cancer Research Center. EL participated on an Advisory Boad of Sanofi Pastuer (unrelated to the topic of the study). RK support for the present mansuscript was funded by NCI U01: U01 CA261277 grant. She received individual consulting fees from Partners in Health. IN, CR, IG, AH, GR, AA, YK, SA, MB, YL, CC, RD and AZ – nothing to declare.
| Funders | Funder number |
|---|---|
| US-CDC | |
| National Institutes of Health | |
| National Cancer Institute | U01CA261277 |
| National Institute of General Medical Sciences | |
| National Institute of Allergy and Infectious Diseases | |
| Pfizer | |
| Merck | |
| University of Virginia | U01: U01 CA261277 |
