Moderna said on 20 December that a booster dose of its COVID-19 vaccine should offer protection against the rapidly spreading omicron variant.

For our comprehensive coverage and latest updates on COVID-19 click here.

Moderna said lab tests showed the half-dose booster shot increased by 37 times the level of so-called neutralising antibodies able to fight omicron. And a full-dose booster was even stronger, triggering an 83-fold jump in antibody levels, although with an increase in the usual side effects, the company said.

While half-dose shots are being used for most Moderna boosters, a full-dose third shot has been recommended for people with weakened immune systems. Moderna announced the preliminary laboratory data in a press release and it hasn't yet undergone scientific review. But testing by the U.S. National Institutes of Health, announced last week by Dr. Anthony Fauci, found a similar jump.

Pfizer's testing likewise found its COVID-19 vaccine triggered a similarly big jump in omicron-fighting antibodies. The vaccines made by Pfizer and by Moderna, both made with mRNA technology, are used by many countries around the world to fight the coronavirus. Together, the available evidence backs health authorities'' increasing pleas for people to get their boosters as soon as they're eligible.

Antibody levels predict how well a vaccine may prevent infection with the coronavirus but they are just one layer of the immune system's defences. Other research suggests the vaccine still should induce good protection against the severe disease if people do experience a breakthrough infection. Both Moderna and Pfizer are developing shots to better match the omicron variant in case they're needed.