(HealthDay News) — Hybrid immunity resulting from previous COVID-19 infection and recent booster vaccination confers the strongest protection against omicron infection, but all forms of immunity protect against severe, critical or fatal COVID-19, according to a study published online June 15 in the New England Journal of Medicine.
Heba N. Altarawneh, M.D., from Weill Cornell Medicine-Qatar in Doha, and colleagues conducted a national, matched, test-negative, case-control study in Qatar to examine the effectiveness of BNT162b2 or mRNA-1273 vaccination, natural immunity due to previous infection with nonomicron variants, and hybrid immunity against symptomatic omicron infection and severe, critical or fatal COVID-19.
The researchers found that the effectiveness of previous infection alone was 46.1% against symptomatic BA.2 infection. Vaccination with two doses of BNT162b2 and no previous infection had negligible effectiveness (−1.1%); the second dose had been received more than six months earlier among nearly all individuals. The effectiveness was 52.2% for three doses of BNT162b2 and no previous infection. The effectiveness was 55.1 and 77.3% for two doses and three doses of BNT162b2, respectively, and previous infection. Strong effectiveness (>70%) was seen against severe, critical or fatal COVID-19 due to BA.2 infection for previous infection alone, BNT162b2 vaccination alone, and hybrid immunity. The results were similar in analyses of effectiveness against BA.1 infection and vaccination with mRNA-1273.
“Recent booster vaccination had moderate effectiveness, whereas hybrid immunity from previous infection and recent booster vaccination conferred the strongest protection against infection, at approximately 80%,” the authors write.
