The Centers for Disease Control and Prevention announced new recommendations for COVID-19 vaccination doses. It was no surprise to many in healthcare that it advised a second dose for those 65 and older or for those younger who are moderately or severely immunocompromised.
What was somewhat unexpected, although positive, is that it now recommends “flexibility for additional doses (i.e., three or more) for those who are moderately or severely immunocompromised, in consultation with their healthcare provider (a strategy known as shared clinical decision making).”
The Advisory Committee on Immunization Practices had discussed such an approach last summer. Some argue that a standard, universal approach is easier for patients and providers to understand. Others advocated for moving toward a risk-based strategy. The CDC still recommends one dose of the 2024-2025 COVID-19 vaccine for people ages 5–64 years who are not immunocompromised.
There had been quite a push from the public for the changes and for a recommendation that everyone get vaccinated every six months instead of yearly. Many urged that immunocompromised people be allowed to get a second COVID-19 vaccine two months after the first.
Over the past four and a half years, we’ve seen that COVID-19 does not have the seasonality that influenza does — waves of infection have occurred year-round. That’s why it made no sense to many to only suggest an annual fall immunization in combination with the flu vaccine.
One of the problems is that there is poor uptake of the vaccines, even when available. Only 22.5% of adults and 14.1% of children received the 2023-2024 vaccine. Fewer than 9% of adults 65 years and older received two or more doses of the 2023-24 COVID-19 vaccine.
Uptake has undoubtedly decreased since then because the CDC’s Bridge Access Program, which provides free COVID-19 vaccines for under- or insured patients, ended in August. Since then, the cost of the vaccine for uninsured people has not been paid for by the government, but has been passed on to individuals, and many can ill afford it.
There is also ample data that the vaccine effectiveness against hospitalization wanes significantly by four to six months in those age 65 years and older. During 2023-2024, vaccine effectiveness against hospitalization in immunocompromised people waned even more, to 0 by about four to six months (p. 17).
One issue is what criteria will have to be met for Medicare/Medicaid or private insurers to cover additional doses for immunocompromised patients. Can patients pay out of pocket if they want an extra dose but don’t meet criteria? If someone is trying to protect an at-risk family member, can they get three or four doses per year covered?
Another interesting recommendation from ACIP is to use vaccines from the same manufacturer (homologous vaccines). This was surprising because, in some earlier studies, a mix-and-match (heterologous) approach seemed advantageous. For example, the FDA noted that heterologous boosters resulted in similar or higher serologic responses than did homologous boosters.
Why is the CDC recommending staying with the same manufacturer now?
Dr. Eric Topol, founder of the Scripps Research Translational Institute, said that perhaps it is because there is a great variability in responses (neutralizing Abs and T cells) to mix-and-match strategy, but no studies showing clearcut differences in clinical outcomes. Another expert hypothesized that it is because the vaccines from different manufacturers target different strains of the virus. Novavax is strongest against the JN.1 lineage, but the mRNA vaccines target the FLiRT variants.
The CDC has not responded to specific, detailed questions about these issues. It’s welcome news that immunocompromised patients can be more protected by flexibility in being allowed more frequent immunizations. But the devil is in the details as to how this can — or will — work in practice. It appears we must await further clarification.