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Novavax Joins Alternative Second Shot Vaccine Trial



15 Apr. 2021. Vaccine developer Novavax is taking part in a clinical trial testing effects of different Covid-19 vaccines in first and second immunizations. The Gaithersburg, Maryland company is joining the clinical trial conducted by the Vaccine Research Group at University of Oxford in the U.K., along with vaccines against the SARS-CoV-2 virus made by BioNTech/Pfizer, Moderna, and Oxford/AstraZeneca.

Most vaccines protecting against the SARS-CoV-2 virus use two doses, a primer dose to prepare the immune system, and a booster dose some weeks later. Vaccines are authorized today to be given to individuals with the same vaccine in both doses, not mixed. And the two-dose vaccines have not yet been tested in humans as mixed combinations. The trial, called Comparing Covid-19 Vaccine Schedule Combinations, or Com-Cov2, aims to discover if the vaccines’ efficacy is different when they’re mixed in the two doses, as well as any adverse effects.

The mid-stage Com-Cov2 trial began in the spring of 2020, with Novavax’s candidate vaccine code-named NVX-CoV2373 now one of the alternatives being tested. NVX-CoV2373 is made with a technology that generates nanoscale particles of synthetic proteins designed specifically against the genetic code of their targets. In this case, the target is the protein on the surface of the SARS-CoV-2 virus’s spike that penetrates and infects host cells. The two-dose vaccine is combined with the company’s vaccine adjuvant called Matrix-M, an additive that boosts immune responses, allowing for lower doses of the primary vaccine.

Enrolling people with one vaccine dose so far

Com-Cov2 is enrolling 1,050 individuals age 50 and over in the U.K. who received their first dose of either the Oxford/AstraZeneca or BioNTech/Pfizer vaccine in the previous eight to 12 weeks, but not their second dose. Each person in both groups is then randomly assigned to receive either the same vaccine or one of the Moderna or Novavax vaccines. The Oxford researchers are looking primarily for production of immunoglobulin G antibodies produced by participants after 28 days. The study team is also tracking local or systemic reactions to the vaccines, as well as adverse effects, immediately and seven days after the shots. And the researchers are measuring T-cell responses from the vaccines, as well as antibodies produced.

“Novavax’s addition to this important study,” says Novavax’s chief medical officer Filip Dubovsky in a company statement, “reflects the urgency of finding innovative ways to protect as many people as possible in a dynamic pandemic landscape. The potential utility of pooling public health resources, including all available vaccines, could help us get ahead of an evolving virus.”

Novavax’s NVX-CoV2373 is being tested in late-stage clinical trials in the U.K., and the U.S. and Mexico. The U.S./Mexico trial began in December 2020 is still ongoing. In the U.K. trial, as reported in Science & Enterprise in January 2021, NVX-CoV2373 recorded an efficacy rate of 96 percent for the original SARS-CoV-2 variant and 86 percent for the B.1.1.7 variant active in the U.K., and now the dominant strain in the U.S. A mid-stage study in South Africa showed an overall efficacy rate of 49 percent against the B.1.35 variant dominant in that country, but 60 percent among individuals testing negative for HIV infections.

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Disclosure: The author owns shares in Pfizer.

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