The Novavax vaccine is 89% effective against Covid-19 in the UK study

However, the vaccine was less effective in a separate intermediate-stage study in South Africa, where another variant has spread. In South Africa, the Novavax injection was about 49.4% effective against Covid-19 in the study. Preliminary results showed that more than 90% of sick individuals for whom sequencing data were available were infected with the new variant circulating in South Africa.

In light of lesser effectiveness in South Africa, Novavax said it has started work on a modified version of its vaccine that better targets the strain identified for the first time and plans to start testing in the second quarter.

Overall, however, the positive performance points to another vaccine soon joining the arsenal of vaccines available in some countries, while health officials struggle against limited supplies as they rush to inoculate residents.

“We now have a vaccine, the first vaccine that has shown effectiveness not only in the original Covid-19 strain prototype, but in two variant strains, one in the UK and one in South Africa,” said Novavax Chief Executive Stanley Erck, in an interview. “It is the only data that shows that we can be effective against all three.”

In the UK study, Novavax said that based on tests performed on 56 of the 62 cases of Covid-19, the vaccine appeared to be 95.6% effective against the original Covid-19 strain and 85.6% against the United Kingdom strain United.

Novavax, which never launched a vaccine on the market, released the results of the study in a press release. The data did not pass standard verification by outside experts that precedes publication in a medical journal.

The Gaithersburg, Maryland, company said it has initiated the process of requesting UK health regulators to release the company’s vaccine use in the country.

Novavax said it will provide the new data to US regulators, which could lead to an authorization until April. But it is possible that US regulators will not decide on the vaccine until they see the results of a third final-stage study that tests the vaccine in the US and Mexico.

The study enrolled 16,000 people, for a target of 30,000, and Novavax said it is possible that the initial results will arrive by the end of March.

Pfizer Vaccines Inc.

and its partner BioNTech SE,

as well as Moderna Inc.,

have been authorized for use in the USA, while a shot from AstraZeneca PLC and the University of Oxford is released in the UK

Novavax has one of the most advanced vaccines in development. Johnson & Johnson too,

who hopes to release the results of the final stage, or Phase 3, tests for his vaccine next week.

The vaccination campaign has taken on a new urgency since the emergence of strains in the United Kingdom and South Africa, in addition to Brazil, threatening to spread more quickly than the old version of the virus and evading some treatments.

The researchers are also trying to see to what extent the vaccines will protect against the new variants and whether Covid-19 drugs will still work.

Moderna Inc. said this week it would develop a booster injection after laboratory tests showed that its Covid-19 vaccine has less of a neutralizing effect against the variant circulating in South Africa.

Moderna and Pfizer said laboratory tests suggest that their vaccines would still be effective against the variants identified in the UK and South Africa. Both variants were detected in the US, as well as the one identified in Brazil.

The Novavax vaccine contains proteins similar to the “peak” proteins found on the surface of the coronavirus.

The researchers designed the spike-like proteins delivered by the injection to trigger an immune response that can later defend against the real coronavirus if a vaccinated person is exposed to it.

Novavax makes proteins in insect cells. The vaccine also contains an adjuvant, designed to increase the immune responses generated by the vaccine, derived from the bark of an evergreen tree native to Chile.

The protein-adjuvant combination is generally similar to the design of some vaccines against other diseases, such as the latest tile injection from GlaxoSmithKline PLC.

Novavax started the main Phase 3 study in the UK in September and involved around 15,000 people.

The study tracked whether adults who received two doses of the vaccine, three weeks apart, experienced mild to severe Covid-19 at a lower rate than study participants who received a placebo, starting one week after the second dose.

The Pfizer-BioNTech and Moderna vaccines were more than 94% effective in Phase 3 trials, while the AstraZeneca vaccine was 62% effective in many study participants.

Novavax said there were “low levels” of serious side effects that were balanced between those who received the vaccine and those who received a placebo in the UK study.

In the smaller South African Phase 2 study, Novavax compared its vaccine to a placebo in about 4,400 people. This study also included a subset of people who were HIV-positive.

If the results of people who are HIV-positive are excluded, the vaccine was about 60% effective, said Novavax.

Health experts believe that the flu vaccine works well if it is 60% effective, although other vaccines can achieve 90% effectiveness. The Food and Drug Administration said Covid-19 vaccines should be at least 50% effective.

The Novavax Phase 3 study of the vaccine in the United States and Mexico began in late December. The start of the test was delayed because Novavax was experiencing some manufacturing problems.

It was the first Covid-19 protein-based vaccine to enter large-scale testing in the United States.

The federal government agreed last July to provide Novavax with $ 1.6 billion to help finance testing and preparations for the manufacture of its vaccine, in addition to purchasing 100 million doses.

In August, the UK government agreed to buy 60 million doses of the Novavax vaccine and collaborate with the company in the Phase 3 study.

Last year, Novavax said that in a small early-stage study of healthy volunteers, his vaccine generated promising immune responses and was generally well tolerated.

If authorized for use, the vaccine could generate sales of US $ 3.45 billion this year, according to an average estimate of analysts surveyed by FactSet.

—Gregory Zuckerman contributed to this article.

Write to Peter Loftus at [email protected]