Moderna's 3-month data raise hopes for COVID-19 vaccine durability

Antibody levels stayed elevated in the 90 days after people received the second dose of Moderna’s COVID-19 vaccine, raising hopes that the prophylactic can provide protection for one year.

With Moderna and Pfizer, in partnership with BioNTech, showing mRNA vaccines provide protection against symptomatic COVID-19 in the short term, attention has turned to durability. The full picture of the durability of protection will only become clear over time, but immunogenicity data from the phase 1/2 trial of Moderna’s mRNA-1273 offer encouragement.

In a letter to The New England Journal of Medicine, scientists at the National Institute of Allergy and Infectious Diseases and other research centers presented updated data on 34 people who received the 100-μg dose of mRNA-1273 in the early-phase trial. The phase 3 trial used the same 100-μg dose.

The researchers tracked a slight decline in levels of binding and neutralizing antibodies over the 90 days after the administration of the second dose. However, the geometric mean titers for both types of antibody remained above the median of a panel of 41 convalescent COVID-19 patients. The median time from diagnosis of contributors to the convalescent panel was 34 days.

Researchers are yet to show what immune characteristics an individual needs to be protected against the coronavirus, limiting our ability to infer the real-world consequences of the antibody increases associated with any vaccine. However, the authors of the NEJM letter said the data show mRNA-1273 “has the potential to provide durable humoral immunity.” Analysts concurred with that assessment.     

In a note to investors, analysts at Jefferies wrote, “mRNA-1273 induced neutralizing antibody levels stay relatively high and decline only modestly over the initial 3 months suggesting the trajectory of protection from symptomatic disease could last for at least 6 mos (though unclear), so an annual boost would seem good."

The NEJM update also touched on the safety of the vaccine. No serious adverse events were seen in the small trial, and no new adverse events deemed related to the vaccine occurred after Day 57. 

Moderna shared details of the NEJM letter alongside an update on its effort to scale up production. As previously disclosed, Moderna expects to make around 20 million doses available in the U.S. by the end of the year. That early delivery is set to be followed by the shipment of up to 125 million vaccines globally in the first quarter. The U.S. will get around 80% of the vaccines available in the first quarter.

“Based on this, we would not be surprised to see the US Govt quickly exercise its option for an additional 100M doses of mRNA-1273, which according to OWS agreement, can be purchased for $1.65B,” the Jefferies analysts wrote.