Effectiveness estimates of three COVID-19 vaccines based on observational data from Puerto Rico

Abstract

Background: On July 15, 2021, with 58% of the population fully vaccinated, the start of a COVID-19 surge was observed in Puerto Rico. On July 22, 2021, the government of Puerto Rico started imposing a series of strict vaccine mandates. Two months later, over 70% of the population was vaccinated, more than in any US state, and laboratory-confirmed SARS-CoV-2 had dropped substantially. The decision to impose mandates, as well as current Department of Health recommendations related to boosters, were guided by the data and the effectiveness estimates presented here.

Methods: Between December 15, 2020, when the vaccination process began in Puerto Rico, and October 15, 2021, 2,276,966 individuals were fully vaccinated against COVID-19. During this period 112,726 laboratory-confirmed SARS-CoV-2 infections were reported. These data permitted us to quantify the outcomes of the immunization campaign and to compare effectiveness of the mRNA-1273 (Moderna), BNT162b2 (Pfizer), and Ad26.COV2.S (J&J) vaccines. We obtained vaccination status, SARS-CoV-2 test results, and COVID-19 hospitalizations and deaths, from the Department of Health. We fit statistical models that adjusted for time-varying incidence rates and age group to estimate vaccine effectiveness, since the time of vaccination, against lab-confirmed SARS-CoV-2 infection, and COVID-19 hospitalization and death.

Results: Two weeks after final dose, the mRNA-1273, BNT162b2, and Ad26.COV2.S vaccines had an effectiveness of 90% (95% CI: 88-91), 87% (85-88), and, 64% (58-69), respectively. After five months, effectiveness waned to about 70%, 50%, and 40%, respectively. We found no evidence that effectiveness was different after the Delta variant became dominant. For those infected, the vaccines provided further protection against COVID-19 hospitalization and deaths across all age groups, and this conditional effect did not wane in time.

Interpretation: The mRNA-1273 and BNT162b2 vaccines were highly effective across all age groups. They were still effective after five months although the protection against SARS-CoV-2 infection waned. The Ad26.COV2.S vaccine was effective but to a lesser degree compared to the mRNA vaccines. Although, conditional on infection, protection against adverse outcomes did not wane, the waning in effectiveness resulted in a decreased protection against serious COVID-19 outcomes across time.

Funding: RAI's work was partly funded by NIH Grant R35GM131802.

Keywords: COVID-19; Observational study; SARS-CoV-2; Vaccines.

Figure 1

Cumulative number of fully vaccinated individuals per day by vaccine manufacturer (represented with different colors).

Figure 2

(Top): SARS-CoV-2 infections (Cases), COVID-19 hospitalizations and deaths per day for individuals 12 years or older during the period of study. (Bottom): Weekly rates (per day per 100,000) for SARS-CoV-2 infections (Cases), COVID-19 hospitalizations and deaths by vaccination status. The rates are based on total numbers and are not adjusted for age. Colors are used to denote the different vaccination status.

Figure 3

Estimated effectiveness plotted against days since the individuals were fully vaccinated. The ribbons represent point-wise 99% confidence intervals. (A) Comparison before and after the Delta variant became dominant by age group and vaccine manufacturer (mRNA-1273 and BNT162b2). (B) Vaccine effectiveness against infections by manufacturer for the entire study period and age groups combined. (C) same as B, but for hospitalizations. (D) same as B but for death.

Figure 4

Estimated probability of adverse outcomes from COVID-19 among individuals with a laboratory-confirmed SARS-CoV-2 infection with 95% confidence intervals. Two vaccinated groups are compared to unvaccinated with the different vaccination manufacturers denoted with color. For Ad26.COV2.S, the estimates and confidence intervals for the 75–84 and 85+ are not shown due to small sizes. (A) Hospitalizations; (B) Deaths.