The mRNA-based vaccines known as BNT162b2 (BioNTech, Pfizer) and mRNA-1273 (Moderna) as well as the single injection vaccine Ad26.COV2.S (Johnson & Johnson) have already been inoculated in nearly 200 million Americans and As some approach the first anniversary of their immunization, questions remain about the long-term efficacy of vaccines.
In a study published in the New England Journal of Medicine , a team of experts from the Beth Israel Deaconess Medical Center (BIDMC) compared the immune responses induced by the three vaccines during an eight-month follow-up period .
The researchers evaluated the 61 participants’ levels of various antibodies, T cells and other immune products from two to four weeks after full immunization , the time of maximum immunity, up to eight months after vaccination. Thirty-one participants received the BNT162b2 vaccine, 22 received the mRNA-1273 vaccine, and eight received the Ad26.COV2.S. vaccine.
Advantages and disadvantages
The mRNA vaccines were characterized by a high peak in antibody responses that declined dramatically at month 6 and declined further at month 8.
The single injection Ad26 vaccine induced lower initial antibody responses, but these responses were generally stable over time with little or no evidence of decline .
The team also found that mRNA-1273 elicited antibody responses that were generally higher and longer lasting than BNT162b2. All three vaccines demonstrated extensive cross-reactivity with variants of SARS-CoV-2, the virus that causes COVID-19.
Thus, although neutralizing antibody levels decline, stable T-cell responses and non-neutralizing antibody functions at 8 months may explain how vaccines continue to provide robust protection against COVID-19 .