Study Suggests Mixing Covid Vaccines Gives Good Protection

Study Suggests Mixing Covid Vaccines Gives Good Protection.

A mix-and-match approach to Covid vaccines – using different brands from different manufacturers for the first and second doses – gives good protection against the pandemic virus, a UK study has found.

The Com-Cov trial looked at the efficacy of either two doses of Pfizer, two of AstraZeneca, or one of them followed by the other and noticed that all combinations worked well, priming the immune system.

This knowledge could offer much more flexibility for vaccine rollout, say experts.

The trial results also hint that people who have already received two doses of AstraZeneca vaccine could have an even stronger immune response if they were given a different jab as a booster if recommended in the autumn.

The UK’s deputy chief medical officer, Prof Jonathan Van-Tam, said there was no reason to change the current successful same dose vaccine schedules in the UK, however, given vaccines were in good supply and saving lives.

However, he says it might be something to look at in the future: “Mixing doses could provide us with even greater flexibility for a booster programme, while also supporting countries who have further to go with their vaccine rollouts, and who may be experiencing supply difficulties.”

Many countries already use mixed doses, Spain and Germany are offering the Pfizer or Moderna mRNA vaccines as a second dose to younger people who have already received a first dose of the AstraZeneca vaccine, this was following concerns about rare but serious blood clots, rather than about efficacy.

Lead investigator Prof Matthew Snape, from the University of Oxford, said the findings did not undermine the UK policy of giving people the same jab twice: “We already know that both standard schedules are very effective against severe disease and hospitalisations, including against the Delta variant when given at eight to 12 weeks apart.”

He said the new results showed mixed dose schedules were also effective, even though the interval of four weeks studied was shorter than the eight to 12-week schedule most commonly used in the UK.

“This longer interval is known to result in a better immune response,” he added.

Mixed dose trial results for a 12-week jab interval will be available next month.

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