Astra Zeneca Covid vaccine ‘as effective’ as Pfizer after 4-5 months, finds study

The Astra Zeneca Covid vaccine is ‘as effective’ as the Pfizer jab after 4-5 months, a UK study has found.

Researchers said being fully vaccinated is still the most effective protection against the Covid-19 Delta variant, which is currently dominant in the UK.

Both doses of the Pfizer vaccine are initially more effective, but efficacy decreases quicker than a double dose of Astra Zeneca. Long-term outcomes need to be looked at, said the study.

Two weeks after the second dose, Pfizer was 93% effective against symptomatic infection, whereas Astra Zeneca was 71%.

Astra Zeneca and Pfizer vaccinations offer ‘good protection’ against new infections of the Delta variant, but this is still less effective compared with the Alpha variant.

The study examined 2.5m test results from 743,526 participants in the UK’s Covid-19 household-infection survey, run by the University of Oxford and the Office for National Statistics.   

Professor Sarah Walker, professor of medical statistics and chief investigator for the survey, said ‘both of these vaccines are still doing very well against Delta… when you start very very high, you’ve got a long way to go’.

Other findings included that the time between jabs has no bearing on the effectiveness of preventing new infections, but younger people will have greater protection from vaccination than older people.

And, people who have had Covid receive even more antibodies once double-vaccinated.

There was insufficient data for Moderna, but the study said a single Moderna dose has ‘similar or greater effectiveness against the Delta variant as single doses of the other vaccines’.

Trial results from earlier this month showed Moderna’s Covid-19 vaccine is still 93% effective six months after the second dose is given.

The study comes as Germany announced this month that it would give a booster mRNA (Pfizer or Moderna) vaccine to anyone who was double-vaccinated with the a vector vaccine (Astra Zeneca or Johnson & Johnson).

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