Figure 2: Incident cases of SARS-CoV-2 infection and prevalence of BNT162b2 vaccination by age group in Israel (Dec 1, 2020, to April 3, 2021)
Graphs show the 7-day daily moving average of laboratory-confirmed SARS-CoV-2 infections and the percentage of the population who had received one and two doses of the vaccine at each time
point in people aged 65 years and older (A), 45–64 years (B), 25–44 years (C), and 16–24 years (D). Note that y-axis scales showing infection incidence differ between age groups.
symptoms later). Although we made efforts to avoid this type of misclassification by excluding the small number of people who were initially reported to be asymptomatic but were later hospitalised for or died from COVID-19, some presymptomatic individuals who later developed symptoms without being hospitalised or dying might still have been included. This type of misclassification, however, was probably uncommon and would be unlikely to substantially influence the vaccine effectiveness estimate against asymptomatic infection. Notably, Israel’s SARS-CoV-2 testing policy was different for unvaccinated and vaccinated individuals during the study period. At 7 days after the second dose, vaccinated individuals were exempt from the SARS-CoV-2 testing required of individuals who either had contact with a laboratory-confirmed case or returned from travel abroad. This testing policy might have resulted in a differential bias that would cause overestimation of vaccine effectiveness against asymptomatic infection (ie, asymptomatic people who received two doses were less likely to be tested than unvaccinated asymptomatic people). However, 19% of the 4·4 million PCR tests conducted during the study period were done on exempted individuals (MoH, unpublished data). Additionally, symptomatic individuals might have been reluctant to report symptoms for fear of being blamed for infecting other individuals, in which case asymptomatic vaccine effectiveness would also be overestimated. Conversely, individuals who were hesitant to receive a COVID-19 vaccine might also have been reluctant to seek SARS-CoV-2 testing, which would lead to underestimation of vaccine effectiveness against asymptomatic infection. Further studies are needed to confirm the magnitude of BNT162b2 protection against
