Two new studies presented at the 2021 AACC Annual Scientific Meeting & Clinical Lab Expo reveal how antibodies against the SARS-CoV-2 virus can vary among recipients of different COVID-19 vaccines and naturally infected individuals, according to a news release from AACC.
Vaccines have become essential tools in the fight against COVID-19, but it’s still unclear exactly how the antibodies generated from different vaccines change or wane over time. Meanwhile, the spread of the Delta variant and the rising number of breakthrough infections have highlighted the importance of characterizing antibodies against SARS-CoV-2 in both vaccinated and unvaccinated individuals.
Researchers led by Michael Kelliher, PhD, of Dartmouth-Hitchcock Medical Center have now shown how antibody responses and adverse reactions can differ in recipients of the Moderna and Pfizer-BioNTech COVID-19 vaccines. In 78 individuals who received Moderna and 70 individuals who received Pfizer,-BioNTech Kelliher’s team collected blood samples before the second vaccine dose, 14 days after the second dose, and 30 days after. The study participants also took a survey where they rated the severity of adverse effects and symptoms after vaccination.
Overall, people who received the Moderna vaccine showed a higher antibody response against the viral spike protein compared with those who received Pfizer (4,244 U/mL vs. 1,986 U/mL 30 days after dose two) and also reported stronger side effects. Kelliher cautions these differences could arise from confounding variables such as the higher mRNA dosage in the Moderna vaccine. His team also found that antibody responses had dropped 30 days after the second dose, regardless of the vaccine given.
A separate research group led by Xiaochun Zhang, MD, PhD, of University Hospitals Cleveland Medical Center, set out to define differences in antibodies against SARS-CoV-2 among vaccinated and unvaccinated people.
The scientists tested for antibodies against the SARS-CoV-2 spike protein, receptor-binding domain (RBD), nucleocapsid protein, and the spike protein’s S1 and S2 subunits in three study groups: 33 fully vaccinated healthcare workers, 52 healthcare workers who had recovered from natural infection, and 34 patients with active infections. The test results revealed that the fully vaccinated individuals had an average of 50-fold higher antibody levels than naturally infected, unvaccinated individuals. Antibodies from the vaccinated group also reacted far more strongly to the RBD and S1 viral antigens, suggesting that antibodies against these proteins could be the best targets for tests developed in the future.
