Real-world effectiveness of homologous and heterologous BNT162b2, CoronaVac, and AZD1222 booster vaccination against Delta and Omicron SARS-CoV-2 infection

ABSTRACT

Given emerging evidence of immune escape in the SARS-CoV-2 Omicron viral variant, and its dominance, effectiveness of heterologous and homologous boosting schedules commonly used in low-to-middle income countries needs to be re-evaluated. We conducted a test-negative design using consolidated national administrative data in Malaysia to compare the effectiveness of homologous and heterologous BNT162b2, CoronaVac, and AZD1222 booster vaccination against SARS-CoV-2 infection in predominant-Delta and predominant-Omicron periods. Across both periods, homologous CoronaVac and AZD1222 boosting demonstrated lower effectiveness than heterologous boosting for CoronaVac and AZD1222 primary vaccination recipients and homologous BNT162b2 boosting. Broadly, marginal effectiveness was smaller by 40–50 percentage points in the Omicron period than the Delta period. Without effective and accessible second-generation vaccines, heterologous boosting using BNT162b2 for inactivated and vectored primary vaccination recipients is preferred.

KEYWORDS:

• SARS-CoV-2
• COVID-19 vaccines
• booster
• vaccine effectiveness
• heterologous booster
• homologous booster

Acknowledgement

The authors would like to thank the Director-General of Health Malaysia for his permission to publish this article. The authors further thank Maheshwara Rao Appannan, MPH, Hazlina Yahaya, DrPH, Shahanizan Mohd Zin, MSc (IHSHM), and Faizah Muhamad Zin, MSc (Community Health) from the Ministry of Health Malaysia for their work with data collection, management, and sharing arrangements.

Disclosure statement

No potential conflict of interest was reported by the author(s).