Research indicates that administering booster shots of bivalent vaccines every three to six months can help enhance a person’s ability to neutralize various SARS-CoV-2 strains, including XBB.1.5.
Individuals who have undergone solid organ transplants and are on immunosuppressant medications to prevent rejection are particularly vulnerable to the severe effects of COVID-19, such as breakthrough infections, serious illness, hospitalization, and death. The XBB.1.5 subvariant of the omicron strain of SARS-CoV-2 has been especially concerning for this group due to its genetic mutation that makes it more transmissible than previous strains.
A recent study published in the journal Clinical Infectious Diseases reveals that regular booster doses of messenger RNA (mRNA) bivalent vaccines can benefit solid organ transplant recipients (SOTRs) and other immunocompromised individuals in combating XBB.1.5 and other SARS-CoV-2 strains.
According to Dr. Andrew Karaba, the senior author of the study and an infectious diseases expert at the Johns Hopkins University School of Medicine, the research showed that the ability of SOTRs to neutralize XBB.1.5 diminishes around three months after the initial bivalent booster shot but improves with a second booster, reaching similar levels as before. This suggests that frequent boosting every six months could help reduce infections, especially in high-risk populations like SOTRs.
Bivalent mRNA vaccines introduce the immune system to spike proteins present in different SARS-CoV-2 strains, which are crucial for the virus to infect healthy cells. Antibodies produced in response to spike proteins in the vaccine can neutralize the virus, preventing infection or reducing its severity.
Dr. William Werbel, a co-author of the study and an infectious diseases expert at the Johns Hopkins University School of Medicine, explained that previous research had shown that a single bivalent vaccine enhanced virus neutralization in immunocompromised individuals, but the duration of this boost was unknown. The study aimed to determine the duration of the boost and assess the effectiveness of a second booster.
The study analyzed 76 SOTRs who had received at least three doses of a primary monovalent mRNA vaccine, received one or two bivalent mRNA vaccine boosters, and provided blood samples before and after the boosters. The participants were mainly middle-aged kidney and/or liver transplant recipients, with some having prior COVID-19 infections.
The results showed a significant increase in antibody levels and virus neutralization a month after the first bivalent booster for the BA.5 and XBB.1.5 strains of SARS-CoV-2. However, these levels decreased by three and six months post-boost. After the second booster, many SOTRs regained the ability to neutralize both strains, although some did not show immunity to XBB.1.5, especially those receiving corticosteroids as part of their medication.
Dr. Karaba emphasized the importance of frequent boosting every three to six months with omicron-containing vaccines to enhance protection against COVID-19, especially for SOTRs and other immunocompromised groups lacking hybrid immunity.
Dr. Werbel noted that this approach has already shown benefits for another high-risk group, individuals aged 65 and above.
The study team, including researchers from Johns Hopkins Medicine like Aura Abedon, Jennifer Alejo, Andrea Cox, Yolanda Eby, Snigdha Panda, Aaron Tobian, Camille Hage, and Scott Johnston, emphasized the need for regular booster vaccines for immunocompromised individuals to improve their COVID-19 defense.
The research was supported by grants from various institutions, and the authors disclosed their financial and conflict-of-interest disclosures.