The Pfizer vaccine against the coronavirus disease (Covid-19) is highly effective (nearly 90 per cent) at preventing hospitalisations from infections of all variants – including Delta – for at least six months after a person has been administered two doses of the said shot, according to a recent study published in The Lancet journal. Researchers found that only the effectiveness of the Pfizer vaccine did not decline significantly over the study period, as opposed to that of other vaccines which declined against all SARS-CoV-2 variants within one month of the two doses being administered. The effectiveness of the Pfizer (BNT162b2) vaccine against hospitalisations remained at 90 per cent overall for all variants, they said.
The study underscores the importance of improving the Covid-19 vaccination rates worldwide and monitoring vaccine effectiveness to determine which populations should be prioritised to receive booster shots, the researchers said.
The study found that vaccine effectiveness against Delta variant infections at one month after two doses of Pfizer was 93 per cent and fell to 53 per cent after four months.
Effectiveness against other variants at one month after receiving two doses was 97 per cent and declined to 67 per cent after four months, the researchers said.
Effectiveness against Delta-related hospitalisations remained high (93 per cent) for the duration of the study period, they said. Researchers did not observe a difference in waning between SAR-CoV-2 variant types.