Moderna begins testing three versions of its COVID-19 vaccine booster in volunteers

Moderna Inc has begun clinical trials of a booster shot of its coronavirus vaccine to see if it provides better protection against the highly contagious variant from South Africa. 

On Wednesday, the first volunteers – who were part of the original clinical trials last year – were given one of three doses.

In a press release, the biotechnology company, which is based in Cambridge, Massachusetts, says it plans to enroll 60 participants in total.

It comes after a study, published in The New England Journal of Medicine, found that Moderna’s two-dose regimen had a six-fold decrease in antibody response against the variant, known as B.1.351.

The variant has not yet become widespread in the U.S., with just 91 cases detected in 21 states, according to the Centers for Disease Control and Prevention (CDC).  

In the U.S., there are 91 confirmed cases of the variant, which is believed to be more resistant to vaccines, across 21 states

Moderna’s vaccine was initially developed in partnership with the National Institutes of Health.

It uses part of the pathogen’s genetic code called messenger RNA, or mRNA, to get the body to recognize the coronavirus and attack it if a person becomes infected.

The candidate, called mRNA-1273, works by tricking the body into producing some of the viral proteins, which the immune system then recognizes and builds a defensive response against.

Trial data revealed the the vaccine was 94.5 percent effective at preventing coronavirus infection and 100 percent effective at preventing severe disease against the originally circulating strains of the virus.

However, recent testing showed the jab produced a weaker immune response against the South African variant, despite still generating enough neutralizing antibodies above the levels needed to be considered protective. 

The trial comes after a study found Moderna’s vaccine had a six-fold decrease in antibody response against the variant (far right) that other common versions of the virus

Several studies suggest B.1.351 is more resistant to existing vaccines than other variants of the coronavirus. 

While Moderna said last month that it believes its original vaccine protects against the variant, but that it would test updates of its jab as a precaution. 

In the new mid-stage – or Phase II – study, volunteers will receive three types of booster shots, which are modified versions of Moderna’s original vaccine. 

One-third of participants will receive 20 micrograms (µg) of the booster candidate, which has been dubbed mRNA-1273.351.

Another-third will receive a higher dose, 50 µg, of the candidate. 

The last group will be given a shot called mRNA-1273.211, which combines Moderna’s original vaccine and the booster shot in one dose. 

If results are positive and the third dose is determined to be safe, Moderna will seek emergency use authorization from the U.S. Food and Drug Administration in the third quarter of 2021.

However, Moderna is not the only vaccine manufacturer that is testing its shot against highly transmissible coronavirus variants.

Last month, Pfizer Inc and its German partner BioNTech SE announced they were also testing a booster shot to see if it generates more immunity against new strains. 

The companies will be offering a third dose to 144 volunteers, all of of whom participated in the vaccine’s Phase I clinical trial in the U.S. last year.  

Health officials in the U.S. have long-stated that the best way to beat the pandemic and prevent variant case numbers from spiking is by vaccinating.

So far, 62.4 million Americans – 18.8 percent of the population – have received at least one dose and 32.9 million – 9.9 percent – are fully immunized, according to the CDC.

An average of about two million people in the U.S. are being vaccinated every day.