Scientists detect delayed and reduced antibody responses after BioNTech/Pfizer COVID-19 vaccination in older adults

By Angela Betsaida B. Laguipo, BSNJun 11 2021

Vaccination efforts have commenced in most countries, prioritizing older adults and those with comorbidities. They are at a higher risk of severe coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogen.

Researchers at the U.S. Centers for Disease Control and Prevention (CDC) detected delayed and reduced antibody and T cell responses after immunization with BNT162b2 or the Pfizer-BioNTech COVID-19 vaccine in older adults compared with healthcare workers in Germany.

Study: Delayed Antibody and T-Cell Response to BNT162b2 Vaccination in the Elderly, Germany. Image Credit: Rido / Shutterstock

The study, which appeared in the CDC’s Emerging Infectious Diseases, highlights the importance of nonpharmaceutical measures, such as regular handwashing, wearing face masks, and physical distancing, even if older adults have already received their vaccines. The team also notes that additional immunizations for the elderly might become necessary.

Vaccination efforts

Worldwide, more than 2.21 billion doses of vaccines have been administered. However, the target of global herd immunity is still some way off.

The SARS-CoV-2 pandemic has warranted the rapid development and rollout of vaccines, especially for those at high risk of severe illness and death, including older adults and those with underlying health conditions.

In December 2020, countries started vaccination efforts to inoculate their residents. One of the first vaccines used was the BNT162b2 or the Pfizer-BioNTech COVID-19 vaccine, which was reported to be more than 90 percent effective starting seven days after the second vaccination dose.

However, only 4.3 percent of the participants in the BNT162b2 efficacy trial were more than 75 years old. Since the elderly have weaker immune responses after immunization, there is a need for further investigation.

The study

The prospective observational cohort study investigated SARS-CoV-2-specific antibodies, maturation of immunoglobulin G (IgG) avidity, and interferon-γ (IFN-γ) release of SARS-CoV-2-specific T cells in two groups of young and elderly Pfizer-BioNTech-vaccinated participants.

The team enrolled participants in two studies performed at Charité–Universitätsmedizin Berlin in Germany. Overall, 123 healthcare workers with an average age of 34 and 71 elderly residents in an assisted living facility with an average age of 81 participated in the study.

The team collected blood samples before the first vaccination schedule (week 0), just before the second vaccination schedule (week 3), and four weeks after the second vaccination schedule (week 7). To distinguish between vaccine-induced antibody response and convalescent SARS-CoV-2 infection, the team used the SeraSpot Anti-SARS-CoV-2 IgG microarray-based immunoassay.

At three weeks, the team found that 93 of 107 of the younger participants demonstrated reactive SARS-CoV-2 receptor-binding domain (RBD) IgG, compared to just 16 of the 52 elderly participants. By the 7^th week, the antibody response rate had increased in both groups. Notably, 64 of the 70 elderly participants showed antibody response.

This shows a marked delay and overall reduced antibody response in older adults, which was confirmed by measuring the functional neutralization capacity using the surrogate virus neutralization test.

Apart from antibody responses, the team also evaluated the SARS-CoV-2 spike-specific T cell responses bn IFN-γ release assay (IGRA) of S1 peptide-stimulated T cells at the 7^th week. The group noted that the number of people with IGRA results was significantly lower in the older participants.

The study findings demonstrate that even though the immune response of the older adults four weeks after the second dose of the Pfizer-BioNTech COVID-19 vaccine has nearly reached the level of younger participants, some of them did not manifest potent antibody and T-cell response.

This suggests that even after receiving the vaccine, some older individuals may still need to be at risk of infection. Health experts recommend implementing infection control measures to prevent infection. The team noted that strategies focused on vaccinating high-risk groups might not be enough to protect those at risk. When an older adult is present in the household, vaccinating the caregivers and close contacts should also be considered.

The study also sheds light on the potential effects of vaccination strategies on the general administration of the first vaccine dose and postponing the second dose. This might leave some older adults with low levels of immunity for a prolonged period. Also, it emphasizes the importance of nonpharmaceutical interventions like using face masks in public places, regular testing, hand hygiene, and physical distancing.