Just as the global vaccination campaign is ramping up, with healthcare providers and state agencies wrestling with the complexity of inoculating millions of citizens, new variants of the SARS-CoV-2 coronavirus are being identified by researchers which may require vaccine developers to update their vaccines periodically. While the most effective method to control the spread of the virus is to vaccinate as many people as possible with existing vaccines, production and supply issues world-wide continue to challenge public health agencies and providers alike.Of concern is the possibility that these emerging variants might reduce the protective effects of two of the leading first-generation vaccines, those produced by Pfizer-BioNTech and Moderna. Both vaccines carry RNA instructions that induce human cells to make the spike protein that the virus uses to infect cells; causing the body to generate antibodies that recognize the spike protein.
Preliminary research conducted at Rockefeller University in New York analyzed blood from a small sample of 20 volunteers who had received two doses of either the Moderna or Pfizer-BioNTech vaccine, found some of these neutralizing antibodies were as effective against viruses carrying certain mutations in the spike protein as they were against widespread forms. However, some of the neutralizing antibodies were only one-third as effective at blocking the mutated variants.
Testing the efficacy of vaccine candidates against new variants will be a complicated matter for those products whose initial trials have concluded and who have received emergency use authorization by the FDA and other regulators. Janssen Pharmaceuticals, owned by Johnson & Johnson on January 29 announced very promising results from their multi-country Phase 3 trial. The company developed a single-dose vaccine and began their Phase 3 trial in September 2020 once several new variants had emerged. As a result, the eight-country study involving almost 44,000 participants was able to demonstrate 66% overall efficacy in preventing moderate to severe COVID-19, 28 days after vaccination. The results noted onset of protection was observed as early as day 14. The level of protection against moderate to severe COVID-19 infection was 72% in the United States, 66% in Latin America and 57% in South Africa, 28 days post-vaccination.
Given only limited research has been conducted to date, scientists are still evaluating if new variants could undercut the effectiveness of the first-generation vaccines. As a result, some vaccine developers are moving forward with plans to update their vaccines to better target the emerging variants such as the ones identified in South Africa, the U.K and Brazil.
Moderna is responding to the origin of new variants by initiating work on its vaccine to match the mutations identified in the South African variant, (referred to as 501Y.V2 or B.1.351 lineage.) The company is also looking into the development of a multivalent vaccine and plans to test if inoculating individuals with a third dose of the existing first-generation vaccine impacts effectiveness against the South African variant.
One potential approach is to replace the original version of the spike protein in the first-generation vaccines with an updated molecule; another is to include both original and new variant versions of the spike protein in a multivalent vaccine.
The seasonal influenza (flu) vaccine is designed to protect against the three or four influenza viruses that research indicates are most likely to spread and cause illness among people during the upcoming flu season, according to the CDC. As flu viruses are constantly changing, the vaccine composition is reviewed each year and updated as needed based on which influenza viruses are making people sick, the extent to which those viruses are spreading, and how well the previous season’s vaccine protects against those viruses.
Clearly, vaccine manufacturers and researchers will be paying close attention to the emergence of new variants in the months ahead. Regardless of the success achieved by the current vaccination effort underway, new variants are continuing to emerge. Recognizing this suggests we are already on a path where COVID-19 vaccines will require updates similar to how seasonal influenza vaccines are revised.
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