PFIZER’S Covid jab is 90 per cent effective for more than six months, a study has confirmed.
Protection against severe illness is still not wearing off even in some of the first people to get the vaccine earlier this year.
Although the risk of catching the virus rises over time as immunity weakens, it stays strong enough to keep most people out of hospital.
Dr Sara Tartof, from the Kaiser Permanente health insurer in the US, said: “Our study confirms that vaccines remain highly effective in preventing severe disease and hospitalisation.”
The medical firm and Pfizer studied real-world medical records from 3.4million people in California.
They found 6.6 per cent of double-jabbed people who caught coronavirus between December and August – 12,130 out of 184,041 – ended up in hospital.
But the results vindicated the UK’s decision to roll out boosters as defences against infection wore off.
The study, published in The Lancet, found jabs prevented 88 per cent of cases for a month after the second dose but only 47 per cent after six months.
More than 22million people in the UK had the Pfizer jab for their first two doses and all over-50s are now being offered it as a booster.
Professor Penny Ward, a medicine expert at King’s College London, said: “If the objective of vaccination is to prevent illness and continued spread of infection, this suggests a need for boosters six months after the first vaccine course.
“This approach has already been adopted in the UK where the booster campaign is now underway.”
