Pfizer and Moderna said that protection from their Covid-19 vaccines can wane over time, as the US drug regulator prepares to consider whether to approve a booster programme.
Ahead of a crucial meeting of the Food and Drug Administration vaccines advisory committee on Friday to discuss its booster proposal, Pfizer submitted a study on Wednesday by Kaiser Permanente Southern California suggesting vaccine efficacy wanes over time naturally, “irrespective of variant”, rather than as a consequence of the Delta strain evading its jab.
Pfizer presented data showing how the vaccine’s protection declined six to eight months after the second dose, becoming gradually less effective in two-month intervals. Vaccine efficacy fell about 6 per cent every two months after the second dose, down from 96.2 per cent a week after full vaccination to 83.7 per cent more than four months later.