Why Did It Take 2.5 Years to Update mRNA Vaccines with Only 2 Additional Variants?

Pharmaceutical companies argued that they used the mRNA platform to quickly update vaccines against new variants. However, the question arises: why did it take 2.5 years to update the vaccines with only two additional variants when there are now over 4,500 known variants?

Why Updates Were Unnecessary

The original vaccines, combined with boosters delivered at least five months after initial inoculation, still provide excellent protection against serious illness or death. This is due to the fact that vaccines stimulate the immune system to produce antibodies that specifically target the variant in question. Additionally, the vaccines train T-cells to recognize a wide range of potential variants, a process known as somatic hypermutation.

Understanding Variant Prevalence

The decision to update the vaccines was largely based on the prevalence of different variants over time. Before mid-2021, there was a significant competition among various variants. The Delta variant emerged later in 2021 and became dominant, but tests showed that existing vaccines against the alpha variant were still effective in preventing serious disease. This lack of a compelling need for a Delta-specific vaccine was a wise choice because by the end of 2021 and into 2022, the Omicron variant became the dominant strain.

The transmissibility of Omicron led to the development of bivalent boosters targeting the original variant and the BA.4 and BA.5 subvariants of Omicron. On June 28, 2022, the FDA's Vaccines and Related Biological Products Advisory Committee approved the addition of the SARS-CoV-2 Omicron component to COVID-19 vaccines used for boosters in the United States. The FDA authorized the bivalent formulations of the Moderna and Pfizer-BioNTech vaccines on August 31, 2022, merely two months later.

The Speed of Vaccine Updates

Two months to update vaccines is exceptionally fast compared to other vaccines, such as the flu, which take at least six months to produce in sufficient quantities. As for the many other variants, most have become extinct. At this time, only Omicron subvariants and Delta remain at very low levels.

Conclusion

The decision to update the vaccines was grounded in careful analysis of variant prevalence and the effectiveness of the existing vaccines. While the process was slow, it was based on sound scientific principles and the goal of protecting public health.

References

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