Distinct Vaccine Efficacy Rates Among Health Care Workers During a COVID-19 Outbreak in Jordan

BACKGROUNDWe aimed to assess the efficacy of 3 COVID-19 vaccines in a population of health care workers at a tertiary cancer center in Amman, Jordan. METHODSWe evaluated the records of 2855 employees who were fully vaccinated with 1 of 3 different vaccines and those of 140 employees who were not vaccinated. We measured the number of SARS-CoV-2 infections that occurred at least 14 days after the second vaccine dose. RESULTSThe 100-day cumulative incidence of PCR-confirmed SARS-CoV-2 infections was 19.3% {+/-} 3.3% for unvaccinated employees and 1.7% {+/-} 0.27% for fully vaccinated employees. The 100-day cumulative infection rates were 0.7% {+/-} 0.22% in BNT162b2 vaccine recipients (n = 1714), 3.6% {+/-} 0.77% in BBIBP-CorV recipients (n = 680), and 2.3% {+/-} 0.73% in ChAdOx1 recipients (n = 456). We used Cox regression analyses to compare the risks of SARS-CoV-2 infection among the different vaccine recipient groups and found a significantly higher infection risk in BBIBP-CorV (hazard ratio [HR] = 2.9 {+/-} 0.31) and ChAdOx1 recipients (HR = 3.0 {+/-} 0.41) compared to BNT162b2 recipients (P = .00039 and .0074, respectively). Vaccinated employees who had no previously confirmed SARS-CoV-2 infections were at a markedly higher risk for breakthrough infections than those who experienced prior infections (HR = 5.7 {+/-} 0.73, P = .0178). CONCLUSIONSOur study offers a real-world example of differential vaccine efficacy among a high-risk population during a national outbreak. We also show the important synergism between a previous SARS-CoV-2 infection and vaccination. FundingNone