After omicron took over, the vaccine's protective effect has diminished.
Although a third dose provides a high level of protection against serious illness in the first three months, the protection against infection has fallen sharply.
Vaccine manufacturers are therefore working to update their covid vaccines so that they provide better protection against omicron and future virus variants.
The modern vaccine candidate targets two different virus strains - both omicron and the original variant from Wuhan.
And the results seem promising so far.
- Data show that we get a significantly higher antibody response to omicron day 29 and that the antibody response to previous covid variants is also higher, says Moderna's drug expert Cesar Sanz Rodriguez.
Does the vaccine also protect against omicron variants?
- We are collecting that information right now, but since the vaccine seems to give a good response to several other covid variants, we predict that it will also protect against omicron variants.
Designed to test safety
The vaccine candidate was evaluated as part of a phase II / III study designed to test the safety and immune response of the vaccine.
It was given to adults as a second booster dose.
The participants had thus already received two doses of Moderna's original vaccine Spikevax and a refill dose.
According to the company, the booster dose was well tolerated by the 437 study participants and the safety was comparable to the original vaccine.
In the coming weeks, Moderna will submit the preliminary analysis and data to regulatory authorities for review.
If the vaccine is approved, it may be on the market in September.