Two doses of J&J, Pfizer vaccines effective against Omicron variantA study of more than 160,000 COVID-19 tests of South African healthcare workers concludes that two doses of the Johnson & Johnson (J&J) and Pfizer/BioNTech vaccines are about 71% effective against hospitalization caused by Omicron 1 to 2 months after the second dose, with little waning at 5 months or longer.Investigators from the South African Medical Research Council led the study, published yesterday in the New England Journal of Medicine (NEJM).
They used a test-negative design to estimate the effectiveness of two doses of the J&J or Pfizer vaccine against hospitalization or intensive care unit (ICU) admission with an Omicron variant infection from Nov 15, 2021, to Jan 14, 2022.The team analyzed the results of 162,637 polymerase chain reaction (PCR) COVID-19 tests, of which 93,854 (57.7%) were from participants given two doses of either the Pfizer vaccine at least 42 days apart or J&J vaccine 4 to 6 months apart.Test positivity was 34%, with 1.6% of patients hospitalized and 0.5% admitted to an ICU.
Among J&J recipients, estimated vaccine effectiveness (VE) against COVID-19 hospitalization was 55% (95% confidence interval [CI], 22% to 74%) by 13 days after the second dose, 74% (95% CI, 57% to 84%) at 14 to 27 days, and 72% (95% CI, 59% to 81%) at 1 or 2 months.Of Pfizer vaccinees, VE was 81% (95% CI, 41% to 94%) by 13 days after the second dose, 88% (95% CI, 62% to 96%) at 14 to 27 days, 70% (95% CI, 64% to 76%) at 1 or 2 months, 71% (95% CI, 68% to 74%) at 3 or 4 months, and 67% (95% CI, 63% to 71%) at 5 or more months.VE against ICU admission in J&J vaccinees was 69% (95% CI, 26% to 87%) at 14 to 27 days and 82% (95% CI, 57% to 93%) at 1 or 2 months