Two doses of the Pfizer Covid-19 vaccine are 90 per cent effective against hospitalisation from the disease for all variants, including Delta, for at least six months, according to a study published in The Lancet journal on Tuesday. The researchers found that over the study period, effectiveness of the vaccine against all SARS-COV-2 infections declined, falling from 88 per cent within one month after receiving two vaccine doses to 47 per cent after six months. However, the effectiveness of Pfizer (BNT162b2) vaccine against hospitalisations remained at 90 per cent overall for all variants, they said. The study underscores the importance of improving Covid-19 vaccination rates worldwide and monitoring vaccine effectiveness to determine which populations should be prioritised to receive booster shots, the researchers said.

“Our study confirms that vaccines are a critical tool for controlling the pandemic and remain highly effective in preventing severe disease and hospitalisation, including from the Delta and other variants of concern,” said the study’s lead author, Sara Tartof from Kaiser Permanente in the US. “Protection against infection does decline in the months following a second dose,” Tartof said.