Effectiveness of different booster regimens for preventing infection and adverse outcomes in Puerto Rico

Recent laboratory and observational studies have demonstrated that the COVID-19 vaccine effectiveness wanes over time. In response, several jurisdictions have authorized the administration of booster doses. Since August 13, 2021, Puerto Rico has administered 540,140 booster shots. We used data collected and made public by the Puerto Rico Department of Health (PRDH) to evaluate the effectiveness of four different booster regimens at preventing SARS-CoV-2 laboratory confirmed infections and adverse COVID-19 outcomes. Specifically, we analyzed data from all 115,995 SARS-CoV-2 infections occurring since the vaccination process commenced on December 15, 2020. We combined vaccination status, SARS-CoV-2 test results, and COVID-19 hospitalizations and deaths data, and fit a statistical model that adjusted for time-varying incidence rates and age group, to estimate time-varying vaccine effectiveness against infection and adverse outcomes. We find that, after 6 months, the mRNA-1273 and BNT162b2 effectiveness against infection wanes substantially to 61% (58%-63%) and 36% (34%-39%), respectively, while the Ad26.COV2.S wanes to 35% (31%-39%) after two months. However, after a booster shot of the corresponding initial vaccine manufacturer, effectiveness increased to 87% (83%-91%) and 82% (79%-85%) for mRNA-1273 and BNT162b2, respectively. The effectiveness for Ad26.COV2.S followed by either a mRNA-1273 or BNT162b2 booster increased to 88% (71%-100%), substantially higher than 65% (59%-70%), the peak effectiveness reached with just one shot. We also found that heterologous booster regimens restored effectiveness. Furthermore, we did not observe waning after two months of the booster shot. Finally, we found that all booster regimens provided increased protection against COVID-19 hospitalizations and deaths. Code and data to reproduce the analyses are provided here: https://github.com/rafalab/booster-eff-pr.