Moderna Inc.'s vaccine still produced signs of immunity to the coronavirus in recipients three months after the second dose, according to phase 1 data published in a letter to The New England Journal of Medicine.
Binding and neutralizing antibodies were detected in patients 90 days after their second 100-microgram dose of the vaccine, called mRNA-1273, researchers said in the Dec. 3 letter. While these antibodies had decreased over time, they were still at high levels in all study participants across all age groups, the researchers said.
The geometric mean titer — or GMT, the average antibody measurement across a group of subjects — was smaller in cohorts aged 56 to 70 years old and 71 years old and older, at 151,761 and 157,946, respectively. In comparison, the GMT of the 18 to 55 age group was 235,228 in the study, which was led by the U.S. National Institute of Allergy and Infectious Diseases.
"Although correlates of protection against SARS-CoV-2 infection 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," said the letter's authors from the NIAID.
Morgan Stanley analysts said in a Dec. 4 note that it is difficult to gather too much from this data given the small cohort of only 34 participants. However, if there are signs of lower antibody levels in older adults, the most at-risk group, then that could support the need for booster shots, analysts said.
Analysts also noted they expect durability data from phase 1, 2 and 3 trials of the vaccine to be made available at the U.S. Food and Drug Administration's Advisory Committee meeting on Dec. 17.
Adaptive immune response
In addition to antibodies, the authors said the vaccine produced a response from helper T cells — cells that coordinate the body's adaptive immune response — 43 days after the first vaccination.
The memory cellular responses to Moderna's vaccine have not been studied yet, but research by other groups has shown that T cells from people who were previously infected with the virus can last for months. Preliminary data from researchers at the U.K.'s Coronavirus Immunology Consortium, Public Health England and Manchester University NHS Foundation Trust found that T cells were present six months after healthcare workers had tested positive for COVID-19.
"When the right T cell finds its match to the virus, it makes copies of itself to strengthen the immune response that it's going to coordinate," Adaptive Biotechnologies Corp. president Julie Rubinstein told S&P Global Market Intelligence in an interview in November.
To coincide with publishing the durability data, Moderna announced that in the first quarter of 2021 the company plans to supply between 100 million and 125 million doses of its vaccine, which demonstrated 94.1% efficacy in a final analysis of phase 3 trial data.