Effectiveness of 1st dose of BNT162b2 vax in reducing SARS-COV-2 13-24 days after immunization

 Gabriel Chodick, PhD1,2 *, Lilac Tene, MSc 1 , Tal Patalon, MD1 , Sivan Gazit, MD1 , Amir Ben Tov, MD 1 , Dani Cohen # , PhD 2 , Khitam Muhsen, PhD# 2

doi: https://doi.org/10.1101/2021.01.27.21250612

Research in context 

Evidence before this study 

We searched PubMed for follow-up studies regarding the effectiveness of BNT162b2 mRNA Covid-19 Vaccine without any language restrictions. The search terms were (BNT162b2 OR mRNA Covid-19 Vaccine) AND (effectiveness OR real-world OR phase IV) until Jan 15, 2021. We found no relevant observational studies among humans. We also assessed Phase II and Phase III clinical trials with BNT162b2 mRNA vaccine. 

Added value of this study 

To our knowledge, this is the first and largest phase IV study on the effectiveness of the BNT162b2 mRNA COVID-19 vaccine in real-world settings. Our findings showed that the first dose of the vaccine is associated with an approximately 51% reduction in the incidence of PCR-confirmed SARS-CoV-2 infections at 13 to 24 days after immunization compared to the rate during the first 12 days. Similar levels of effectiveness were found across age groups, sex, as well as among individuals residing in Arab or ultra-orthodox Jewish communities that display an increased COVID-19 risk. 

Implications of all the available evidence

 The study results indicate that in real life the first dose of the new BNT162b2 mRNA COVID19 vaccine confers around 50% protection against overall SARS-CoV-2 infections (symptomatic or asymptomatic). Together our findings and the 95% efficacy shown in the phase III trial, suggest that the BNT162b2 vaccine should be administered in two doses to achieve maximum protection and impact in terms of disease burden reduction and possibly reducing SARS-CoV-2 transmission. COVID-19 vaccines should be urgently deployed globally.

 Abstract 

Background 

BNT162b2 vaccines showed high efficacy against COVID-19 in a randomised controlled phase-III trial. A vaccine effectiveness evaluation in real life settings is urgently needed, especially given the global disease surge. Hence, we assessed the short-term effectiveness of the first dose of BNT162b2-vaccine against SARS-CoV-2 infection. Given the BNT162b2 Phase-III results, we hypothesized that the cumulative incidence of SARS-CoV-2 infection among vaccinees will decline after 12 days following immunization compared to the incidence during the preceding days.

Methods 

We conducted a retrospective cohort study using data from 2·6 million-member state-mandated health provider in Israel. Study population consisted of all members aged 16 or above years who were vaccinated with BNT162b2-vaccine between December/19/2020 and January/15/2021. We collected information regarding medical history and positive SARSCoV-2 polymerase chain reaction test from days after first dose to January/17/2021. Daily and cumulative infection rates in days 13-24 were compared to days 1-12 after first dose using Kaplan-Meier survival analysis and generalized linear models.

Findings 

Data of 503,875 individuals (mean age 59·7 years SD=14·7, 47·8% males) were analysed, of whom 351,897 had 13-24 days of follow-up. The cumulative incidence of SARS-CoV-2 infection was 0·57% (n=2484) during days 1-12 and 0·27% (n=614) in days 13-24. A 51·4% relative risk reduction (RRR) was calculated in weighted-average daily incidence of SARSCoV-2 infection from 43·41-per-100,000(SE=12·07) in days 1-12 to 21·08-per100,000(SE=6·16) in days 13-24 following immunization. The decrement in incidence was evident from day 18 after first dose. Similar RRRs were calculated in individuals aged 60 or  above (44.5%), younger individuals (50.2%), females (50.0%) and males (52.1%). Findings were similar in sub-populations and patients with various comorbidities. 

Conclusions 

We demonstrated an effectiveness of 51% of BNT162b2 vaccine against SARS-CoV-2 infection 13-24 days after immunization with the first dose. Immunization with the second dose should be continued to attain the anticipated protection.

https://www.medrxiv.org/content/10.1101/2021.01.27.21250612v1.full.pdf