Medical Technology

Drop in COVID Vaccine Effectiveness suggests the need for boosters

Editor’s Note: Medscape’s Coronavirus Resource Center has the most up-to-date COVID-19 news.

A new study found that the effectiveness of the COVID-19 vaccines was less effective in older patients. This suggests that booster doses may be required to protect patients for the long-term.

The same was the case for the group of US veterans, with an average age of 67 years. Also those who received “the Moderna vaccine consistently had lower levels of antibody, when compared to recipients of the Pfizer BioNTech vaccine, across all age groups and time between vaccinations,” Kristina L. Bjema, MD of the CDC’s COVID-19 response team, and their colleagues.

The effectiveness of the Moderna vaccine was 89.6 percent at 14 to 119 days after patients had received the second dose, compared to 86.0 percent for the Pfizer vaccine. After 120 or more days, the vaccine effectiveness had dropped to 86.1 percent for Moderna and 75.1% for Pfizer as reported by the investigators in the Morbidity and Mortality Weekly Report.

The levels of the relevant antibodies, such as anti-spike immunoglobulin IgG and anti-receptor bindingdomain (RBD IgG), showed the same pattern. They were lower after the 120-day mark for each vaccine, however they were higher at both the Moderna and Pfizer time frames. These differences in antibody levels are in line with other studies, according to researchers and could be the result of the Moderna vaccine’s higher antigen content and its longer interval between doses.

All veterans of 1896 who participated in the study were included as they were being treated for COVID-like illnesses at five Veterans Affairs medical centers across the country (Atlanta and Houston, Los Angeles, New York City, New York City, Palo Alto, California). The group comprised patients who tested positive and those who were not positive for COVID-19 at the time they were first hospitalized. 799 of them eventually were fully vaccine-free. The average age of 58% participants was 65 years old or more.

Both vaccines were more effective in younger patients: 89.4% in the Pfizer group for patients who are less than 65 years of age, and 72.9 percent for those aged 65 and older in the Pfizer group. This is in contrast to Moderna’s 94.5 % and 78.6 percent. Researchers observed that both groups experienced the same decline in effectiveness after 120 days.

The effects of aging can be cause for concern.

“Overall for both vaccine products the levels of antibodies in this group of older US veterans with high prevalences of underlying medical conditions were significantly lower than those observed in healthy, younger volunteers or healthcare personnel in other studies,” they said, noting that booster doses could be needed “to provide long-term protection from severe COVID-19.”

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