The company said that when compared with the placebo group, the vaccine was 66 percent effective at preventing moderate to severe cases, and 85 percent at preventing severe cases.

On Friday, AstraZeneca's Covid-19 vaccine was recommended for conditional marketing authorisation (CMA) in the European Union.

In clinical trials, the Novavax jab showed an overall efficacy of 90 percent against COVID-19, as well as 86 percent protection against the variant first found in the United Kingdom and 60 percent protection against the strain discovered in South Africa. It said the candidate demonstrated "complete protection" against Covid-related hospitalization and death, 28 days post-vaccination.

Both Pfizer and Moderna's shots are impressive vaccines, touting efficacies higher than 94% in clinical trials of tens of thousands of people in the USA and around the world. "If it prevents me from going to the hospital, I'm all for it". So far, the mutants haven't overwhelmed the protective power of vaccines.

The trial was conducted in eight countries grouped into three regions.

Fauci said this finding makes the case even stronger for as many people to get vaccinated as quickly as possible to prevent the spread of this and other variants from other countries - as well as new variants arising in the USA, which he said are occurring in high-prevalence areas such as Los Angeles and the state of California.

The efficacy rate of Janssen's vaccine is lower than the 94-95% effective Moderna and Pfizer-BioNTech vaccines already authorized in the USA, but investigators said there are key differences that make Janssen's vaccine valuable.

"It's really a wake-up call for us", Dr. Anthony Fauci said.

"First of all the volume to get more vaccine". He says they expect at least single doses to be administered by the end of next month.

Corbett was instrumental in developing Moderna's new mRNA COVID-19 vaccine, which (along with Pfizer's vaccine) is one of two vaccines authorized for emergency use to fight the pandemic in the US.

Location: If it's approved, the vaccine will be manufactured in the UK.

Two more vaccines from American companies are nearing the stage where the FDA can evaluate them for approval.

The company said 9 percent of volunteers developed a fever shortly after the injection. Moderna's trial for ages 12-17 is still recruiting.

Moderna, a USA biotechnology company, said earlier this week that its vaccine is expected to be protective against the variants, but that it is advancing a vaccine booster candidate against the South African strain into preclinical studies. However, there were no cases of anaphylaxis detected in those trials either; the rare cases began emerging once the vaccines hit the market. Also, all packages of the Pfizer vaccine now getting shipped out contain low dead-volume syringes to maximize the number of doses that can be obtained from each vial, Slavitt said. Some experts suspect a compound in the fatty bubble used to transport the mRNA might cause the reactions, particularly one called polyethylene glycol or PEG.