Following preliminary data that showed the AstraZeneca/Oxford COVID-19 vaccine to have minimal effect in preventing mild to moderate cases of a South African variant, the global COVAX initiative has nevertheless stressed the need to assess its efficacy against more severe illness.
Preliminary data from phase three trials excluding the South African variant (B.1.351) have shown that the vaccine offers protection against severe disease, hospitalization, and death. In those cases, its overall efficacy was 76 percent after a first dose, which increased to 82 percent with an inter-dose interval of 12 weeks or more. This shows the vaccine may still have some role to play in the fight against the South African variant, and certainly, the COVID-19 epidemic at large.
COVAX also stressed that the study that revealed the vaccine’s low efficacy against the South African variant used a limited size focused on low-risk participants and interval doses not optimized for immunogenicity.
“Additional studies will also allow us to confirm the optimal vaccination schedule and its impact on vaccine efficacy,” COVAX said in a statement. “CEPI has announced funding for additional clinical research to optimize and extend the use of existing vaccines, which could include “mix-and-match” studies of different vaccines used in combinations that may improve the quality and strength of the immune response. Such studies could be useful in optimizing the use of available vaccines, including the AstraZeneca/Oxford vaccine.”
It should be noted that the COVAX facility has signed advance purchase agreements with AstraZeneca and Serum Institute of India and published plans to distribute nearly 350 million doses in the first half of the year. The World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization (SAGE) also met this week to review evidence on the AstraZeneca/Oxford vaccine, including its efficacy against viral variants.
COVAX has urged manufacturers to be prepared to adjust to any evolutions of SARS-CoV-2, the virus that causes COVID-19. Trials should also be designed and maintained to allow for changes in efficacy to be assessed while the world pushes toward greater coordination and response, mainly through greater sharing of genetic and meta-data, paired with enhanced genomic surveillance.
“The emergence of variants of SARS-CoV-2, the virus that causes COVID-19, serve as a powerful reminder that viruses by their very nature mutate and that the scientific response may need to adapt if they are to remain effective against them,” COVAX said.