Possible Link Between RSV Vaccines and Guillain-Barré Syndrome Raises Concerns
In a recent meeting of the Advisory Committee on Immunization Practices, vaccine safety experts from the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) presented data suggesting a possible link between RSV vaccines and Guillain-Barré syndrome (GBS). The data showed an elevated rate of GBS among individuals who received the Pfizer vaccine, although cases were also detected among those who received the GSK product.
However, the experts emphasized that it is still too early to determine if there is a true increased risk of developing GBS after RSV vaccination or to quantify the size of that risk. Tom Shimabukuro, former director of the CDC’s immunization safety office, stated that the data and findings are based on small numbers of cases and doses administered, making it difficult to establish a conclusive link at this stage.
The CDC plans to conduct a more in-depth analysis using a different vaccine safety database in March, which will provide better risk estimates in the coming weeks and months. GBS is a neurological condition characterized by muscle weakness and paralysis, with most people recovering over time but some experiencing permanent nerve damage. It is more common in individuals aged 50 and older, with two-thirds of cases developing shortly after infection with a virus or bacterium that causes respiratory illness or diarrhea.
While some vaccines have been associated with an increased risk of GBS, determining a true link can be challenging. Additionally, even if there is an increased risk following vaccination, it must be assessed in a broader context. For example, although there may be a small increased risk of GBS after flu vaccination, it is known that contracting the flu itself also increases the risk of developing GBS.
Concerns about the new RSV vaccines arose after three cases of GBS were detected during clinical trials conducted by Pfizer and GSK to obtain FDA licensure. Vaccine safety analysts at the CDC and FDA have been monitoring safety databases, including the Vaccine Adverse Events Reporting System (VAERS), to identify any potential safety signals following the initial rollout of the RSV vaccines.
As of mid-February, CDC analysts had verified 23 cases of GBS among approximately 9.5 million vaccinated individuals. Of these cases, 15 were linked to the Pfizer vaccine, and eight were associated with the GSK vaccine. It is worth noting that 14 of the cases involved individuals who received the RSV vaccine alongside other vaccines, such as flu shots, COVID-19 vaccines, shingles vaccine, tetanus-diphtheria and pertussis vaccine, and a rabies shot.
The rate of GBS cases within 21 days of vaccination was 4.6 per 1 million doses for Pfizer recipients and 1.1 per 1 million doses for GSK recipients. The expected background rate for GBS among individuals receiving vaccines without an elevated risk is 2.0 cases per 1 million doses. Pfizer and GSK are conducting post-marketing safety studies to further assess the risk of GBS among vaccine recipients.
Both Pfizer and GSK maintain that their vaccines are safe. Reema Mehta, Pfizer’s vice president and head of risk assessment and management for worldwide safety, stated that the company will continue to share findings from its post-marketing studies with the CDC, FDA, and other stakeholders. GSK spokeswoman Alison Hunt noted that the CDC analysis did not suggest an elevated rate of GBS among individuals who received the company’s RSV vaccine. GSK is currently designing a study to evaluate the risk of GBS after receiving their vaccine.
Despite the potential link to GBS, CDC vaccine experts continue to support the use of RSV vaccines in individuals aged 60 and older due to the burden of RSV disease in that population. The agency estimates that for every 1 million doses of RSV vaccine administered, thousands of hospitalizations, intensive care unit admissions, and deaths related to RSV are averted.
The emergence of this signal coincides with GSK’s efforts to expand the license for its RSV vaccine by lowering the age eligibility to include individuals aged 50 to 59 with underlying health conditions. The ACIP’s RSV work group is also considering changing the CDC’s recommendation on who should receive an RSV vaccine. The current policy recommends vaccination for individuals aged 60 and older based on shared decision-making between the healthcare provider and the patient. However, this recommendation has caused confusion among physicians and potential recipients, potentially impacting vaccine uptake.
Amadea Britton, a CDC expert involved in the RSV work group, revealed that the group is contemplating a universal recommendation for some adults, possibly those aged 75 and older. This would simplify the recommendation process and ensure that individuals in that age group receive the vaccine. Recommendations for younger age groups would still be based on individual risk and require a healthcare provider’s recommendation.
In conclusion, while the data suggests a possible
