Correlation of SARS-CoV-2-breakthrough infections to time-from-vaccine

Abstract

The short-term effectiveness of a two-dose regimen of the BioNTech/Pfizer mRNA BNT162b2 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine was widely demonstrated. However, long term effectiveness is still unknown. Leveraging the centralized computerized database of Maccabi Healthcare Services (MHS), we assessed the correlation between time-from-vaccine and incidence of breakthrough infection between June 1 and July 27, the date of analysis. After controlling for potential confounders as age and comorbidities, we found a significant 1.51 fold (95% CI, 1.38-1.66) increased risk for infection for early vaccinees compared to those vaccinated later that was similar across all ages groups. The increased risk reached 2.26- fold (95% CI, 1.80-3.01) when comparing those who were vaccinated in January to those vaccinated in April. This preliminary finding of vaccine waning as a factor of time from vaccince should prompt further investigations into long-term protection against different strains.

Fig. 1. Crude breakthrough infections by month of vaccination.

The crude incidence rates per 10,000 individuals above the age of 16 are shown by the month of administration of the second dose of the vaccine; bars represent 95% confidence intervals.

Fig. 2. Accumulative breakthorough infections and hospitalizations among Early and Late Vaccinnes during June - July 2021, Israel.

Kaplan–Meier curves are used for the accumulative probability of breakthrough infection (a) and hospitalization (b) between June and July 2021 among individuals who were vaccinated Early (January to February 2021) compared with individuals who were vaccinated late (March to April 2021). X axis in curves a, b represents days from the start of the follow-up period (June 1, 2021). Shading illustrates 95% CIs (a, b).