Published Phase I Results Hint at Durability of Moderna's COVID-19 Vaccine

Because human testing of the various COVID-19 vaccines has not been going on very long, there are still many open questions about the durability of the vaccines’ immune response. In other words, how long will the effects of the vaccines last? Weeks, months, years? It’s too early to know, but researchers with the U.S. National Institute of Allergy & Infectious Diseases (NIAID) published a letter in The New England Journal of Medicine describing the three-month immunogenicity levels in Moderna’s mRNA-1273 vaccine.

The results were from the Phase I trial of the vaccine. They described immunogenicity data 119 days after the first shot, which was 90 days after the second shot, in 34 healthy adult volunteers. They received two injections of the vaccine at a dose of 100 micrograms 28 days apart.

They found high levels of binding and neutralizing antibodies that decreased slightly over time, which was expected. But in all participants, those levels were still high three months after the second vaccination. They also stratified the responses by age, by those 18 to 55 years of age, 56 to 70 years of age, and 71 years and older. Serum neutralizing antibodies were detected in all participants at day 119.

They conclude, “Although correlates of protection against SARS-CoV-2 injection in humans are not yet established, these results show that despite a slight expected decline in titers of binding and neutralizing antibodies, mRNA-1273 has the potential to provide durable humoral immunity.”

Overall, the antibody response was higher than seen in a panel of 41 convalescent COVID-19 patients—that is to say, people who had and recovered from COVID-19.

The researchers noted that for the “memory cellular response,” the vaccine resulted in the development of primary CD4 type 1 helper T responses 43 days after the first shot and they were still conducting vaccine-induced B-cell studies.

“Longitudinal vaccine responses are critically important,” they write, “and follow-up analysis to assess safety and immunogenicity in the participants for a period of 13 months is ongoing. Our findings provide support for the use of a 100-microgram dose of mRNA-1273 in an ongoing Phase III trial, which has recently shown a 94.5% efficacy rate in an interim analysis.”

Although perhaps this is guesswork based on the data, analysts with Jefferies wrote in a note to investors, “mRNA-1273 induced neutralizing antibody levels stay relatively high and decline only modestly over the initial three months suggesting the trajectory of protection from symptomatic disease could last for at least six months (though unclear), so an annual boost would seem good.”

If that is the case, then COVID-19 vaccinations could become like influenza shots, with yearly shots required.

Moderna also provided an update on its vaccine development. They have submitted the data to the U.S. Food and Drug Administration (FDA) for emergency use authorization (EUA) and have a vaccines advisory committee meeting scheduled for December 17. Potentially the vaccine could receive approval on that date or shortly thereafter and begin immediate distribution.

The company said it plans to have about 20 million doses available in the U.S. by the end of the year, with between 100 million and 125 million doses available in the first quarter of 2021 globally, with 85 to 100 million available for the U.S. market and 15 to 25 million outside the U.S. Overall in 2021, they expect to manufacture 500 to 1 billion doses in 2021.

Currently, the Pfizer-BioNTech vaccine, which uses the same technology as the Moderna vaccine, has been granted emergency authorization in the UK and has a vaccines advisory panel scheduled with the FDA next week on December 8, 9 and 10 and potentially could grant approval on December 10, or within a few days afterward.

Pfizer-BioNTech had originally planned to roll out 100 million vaccines globally by the end of this year, but are now saying 50 million. They still believe they can manufacture more than a billion doses in 2021, enough for about 500 million people. The downgrade of this year’s 100-million-dose goal to 50 million was caused by supply-chain issues.

At this point, Pfizer and BioNTech believe they are on schedule to deliver 1.3 billion vaccine doses in 2021, with the 50 million shortfall for 2020 being handled as manufacturing gets going.

The U.S. government’s initial order was for 100 million with the option to acquire another 500 million. The EU ordered 200 million with an option for another 100 million. Japan ordered 120 million and countries in South America and in the Asia-Pacific region “also have placed significant orders.”