4th dose of COVID vaccine gives big boost, study says

(CNN) - New research has been published on fourth doses of mRNA COVID-19 vaccines.

A study found a fourth dose of Moderna or Pfizer’s vaccine seems safe and provides a “substantial” boost to immunity at similar or even better levels than a third dose.

A fourth dose is already authorized in the U.S. for people 50 and older.

Participants in a UK study had a median age just over 70 years old.

They were given a half dose of Moderna or a full dose of Pfizer in January, about seven months after their first booster.

The second booster didn’t appear to have any major side effects.

The biggest complaints were arm pain and fatigue.

The booster generated an immune response at day 14 that was higher than that at day 28 after the third dose.

Researchers found Moderna’s fourth dose seemed to do slightly better than Pfizer’s, but it’s not clear why.

The study was published Monday in the medical journal The Lancet.

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