December 10, 2021 – Efficiency of the two most common COVID-19 vaccines it decreased over time in the elderly group of patients, suggesting that dose doses might be needed for long-term protection of the recipient, according to a new study.
It can also be seen in that group of American veterans, who had an average age of 67: those receiving the “Modern vaccine consistently had higher levels of antibodies, compared to recipients of Pfizer-BioNTech, in all age groups and time since vaccination, ”said Kristina L. Bajema, MD, of the CDC’s COVID-19 response team and co-workers. .
The effectiveness of Moderna was 89.6% 14-119 days after patients received the second dose, compared with 86.0% for Pfizer. After 120 or more days, vaccine effectiveness fell to 86.1% for Modern and 75.1% for Pfizer, researchers in Weekly Morbidity and Mortality Report.
Levels of relevant antibodies – anti-spike immunoglobulin (IgG) and antireceptor binding domain (RBD) IgG – showed a similar pattern: lower after the 120-day mark for both vaccines, but higher in both time periods for Modern than for Pfizer. These differences in antibody levels are consistent with other studies, the researchers said, and may be the result of higher antigen content in the Moderna vaccine and a longer dose interval.
All 1896 veterans in the study were included as they were hospitalized with COVID-like disease at five veterans medical centers nationwide (Atlanta, Houston, Los Angeles, New York City, and Palo Alto, CA). The group included patients who were positive and those who were negative for COVID-19 when they were first hospitalized; 799 were eventually fully vaccinated. About 58% of the group was 65 or older.
Both vaccines were more effective in younger patients: 89.4% for those under 65 and 72.9% for those 65 and older in the Pfizer group, compared with 94.5% and 78.6% for Moderna, respectively. The same decrease in efficiency after 120 days was recorded for both age groups, the researchers noted.
The effect of age can be a cause for concern.
“Overall, for both vaccine products, antibody levels in this group of older U.S. veterans with a high prevalence of underlying health conditions were significantly lower than those observed among younger, healthy volunteers or health personnel in other studies,” they said, adding that the booster may be needed “to help maintain long-term protection against severe COVID-19”.