A selection of independent, expert advisors for the Food and Drug Administration voted overwhelmingly to approve the two-dose Novavax Covid-19 vaccine yesterday, with 21 of 22 committee members voting for the vaccine and one member abstaining.
The approval is for a two-dose primary series for adults only, not for boosters. The FDA is not required to follow the advice of its committee Advisory Committee on Vaccines and Related Biological Products (VRBPAC) – but the agency typically follows their advice. If the FDA approves the vaccine, the Centers for Disease Control and Prevention must sign the use before it becomes available.
The decision regarding the Novavax vaccine, which has already been approved in dozens of other countries, is not straightforward in the United States. The vaccine has some advantages over currently approved vaccines, but has several strikes against it.
In terms of design, the vaccine follows a more traditional recipe than the two mRNA-based Covid-19 vaccines or Johnson & Johnson’s adenovirus vector-based designs. Both of these designs are relatively new and work by delivering genetic code for the SARS-CoV-2 spike protein to our cells, which then translates the code. The Novavax vaccine, on the other hand, is a protein subunit-based vaccine that directly delivers the SARS-CoV-2 tip protein to cells along with an adjuvant – an additive used in vaccines to enhance the immune response to the vaccine. In this case, the adjuvant is derived from saponin compounds found in the Chilean soapbark tree, which has previously been used in FDA-approved vaccines.
In general, the protein subunit vaccine design is tested and reliable; it is already used in vaccines against, for example, influenza, pertussis and meningococcal infection.
Who would get it?
Novavax leaned heavily into the traditional design in its pitch to the FDA. Now that we’re more than two years into the pandemic and mRNA vaccines are readily available in the United States, most people who want to be vaccinated have already had their shots fired. This raises a key question as to what role Novavax’s vaccine has left behind and how it justifies “emergency use” given the availability of other vaccines.
The company aimed its traditional shots at vaccine holdouts, which the CDC estimates count at around 27 million. They may be wary of the more innovative mRNA vaccines, but they could finally be influenced to be vaccinated if offered an alternative that is perceived as more conventional, Novavax claimed.
“Millions of Americans today are still unvaccinated,” said Greg Poland, director of the Mayo Vaccine Research Group, who spoke on behalf of the Novavax vaccine at yesterday’s meeting. “For those who are not fully vaccinated and are waiting for another option, having a vaccine platform like several stakeholders – including regulators, doctors and the general public – can alleviate some of the challenges we face today. – is familiar with.”
Although some committee members were skeptical that another option would affect the wait, top FDA vaccine regulator Peter Marks seemed to buy it. “We have a vaccine problem that is very serious in the United States, and all we can do to make people more comfortable accepting these potentially life-saving medical products is something we feel compelled to do. “said Marks. He also noted that some Americans are unable to get mRNA vaccines due to side effects, and therefore the protein-based vaccine would be a welcome new option.
Efficiency, variants and safety
Novavax’s vaccine had solid efficacy estimates in a clinical trial published in February in New England Journal of Medicine. In the trial of more than 29,000 participants, the vaccine had an overall efficacy estimate of 90.4 percent against symptomatic Covid-19. The safety data of the vaccine suggest that it is generally safe and well tolerated, although there may be an association with rare cases of myocarditis seen with the mRNA vaccines.
That said, the trial was completed last year before Delta and Omicron (with all its sub-variants) came out. It is unclear how the effectiveness of the vaccine will stand up to the newer variants.