A recent study from Johns Hopkins Medicine has revealed that older adults with weakened immune systems may not respond as strongly to respiratory syncytial virus (RSV) vaccines as their immunocompetent peers. The research, published in JAMA, highlights the need for optimized vaccination strategies for this vulnerable population.
The study focused on 38 adults aged 64-72 with self-reported immunocompromising conditions who had received either the RSVPreF3-AS01E (Arexvy) or RSVpreF (Abrysvo) vaccine. Researchers assessed the participants' antibody responses to the vaccines, finding a heterogeneous response compared to the robust seroconversion rates observed in immunocompetent individuals during vaccine trials.
Key Findings on Antibody Response
The study found that preF IgG antibody titers rose a median of 4.21-fold by 4 weeks post-vaccination, with only 61% of the immunocompromised group meeting seroconversion criteria. This is in stark contrast to the universal seroconversion and greater than 10-fold rises in preF IgG typically seen in immunocompetent individuals. Furthermore, approximately 40% of immunocompromised participants did not seroconvert or achieve a conservative neutralization threshold after vaccination.
Median 4-week NT50 fold rise was 6.97, and 58% achieved high-titer neutralization. Baseline NT50 rose from 395 to 2,978 at 4 weeks post-vaccine.
Impact of Adjuvants on Vaccine Response
Researchers also investigated the potential impact of vaccine adjuvants on immune response. Arexvy, an adjuvanted vaccine, was compared to Abrysvo, which does not contain an adjuvant. The study indicated that participants who received Arexvy tended to have higher levels of RSV-neutralizing, anti-pre-fusion F antibodies.
"When we compared the antibody responses between those study participants who received Arexvy with those who got Abrysvo, we found that the group receiving the adjuvanted vaccine tended to have higher levels of RSV-neutralizing, anti-pre-fusion F antibodies," said William Werbel, MD, PhD, assistant professor of medicine at the Johns Hopkins University School of Medicine.
Implications for Immunocompromised Individuals
These findings suggest that the presence of an adjuvant may play a crucial role in enhancing immune response to RSV vaccines in immunocompromised individuals. Low antibody titers may indicate a role for additional vaccine doses to enhance immune response among immunocompromised persons
Despite the weaker responses observed in some participants, the researchers emphasize that the study does not suggest RSV vaccines will not reduce RSV disease in people who are immunocompromised. The CDC currently recommends a single dose of an RSV vaccine for people 75 and older, as well as those 60 and older who are at high risk, including immunocompromised individuals.
Study Limitations and Future Directions
The study authors acknowledged several limitations, including the small sample size, the absence of cellular data, and the lack of correlations with vaccine effectiveness. Future research should focus on larger, more comprehensive studies to further investigate the role of adjuvant-enhanced vaccines and optimize vaccination strategies for immunocompromised individuals.
"As with our previous work with COVID-19 vaccines [which led to recommendation that people who are immunocompromised getting additional vaccine doses to improve protection], we look forward to additional research on RSV vaccine responses that will provide guidance for optimized timing and vaccine selection for people who are immunocompromised," says Andrew Karaba, M.D., Ph.D., study lead author, assistant professor of medicine, Johns Hopkins University School of Medicine.
