COVID-19 vaccine effectiveness against hospitalization turned negative over time, according to U.S. Centers for Disease Control and Prevention (CDC) data presented on June 15.
The effectiveness against hospitalization plummeted to negative 8 percent for people who received one of the old COVID-19 vaccines, according to data from a CDC-run hospital network.
A dose of one of the updated bivalent vaccines moved the protection above zero, to 29 percent, but the protection fell back to negative 8 percent beyond 89 days, the data show.
The protection estimates were for adults without a compromised immune system from Jan. 23 to May 24, when the XBB strain was dominant in the United States. The data came from people hospitalized at one of 25 hospitals across 20 states that are part of the Investigating Respiratory Viruses in the Acutely Ill network. Both cases and controls were hospitalized with COVID-like illness but the cases tested positive for COVID-19 and the controls tested negative for COVID-19.
“We see a pattern of waning against hospitalization,” Dr. Ruth Link-Gelles of the CDC said while presenting the data to a U.S. Food and Drug Administration (FDA) panel as they consider updating the composition of the vaccines.
Link-Gelles didn’t specifically comment on how the effectiveness turned negative but noted the wide confidence intervals for some of the effectiveness estimates.
The bivalent vaccines, made by Moderna and Pfizer, were introduced in the fall of 2022 with the hopes of improving protection against hospitalization and death after the old vaccines proved increasingly incapable of providing sustained shielding.
Dr. Robert Malone, who helped invent the messenger RNA technology utilized by the vaccine companies in their vaccines, said that the negative effectiveness is consistent with prior data such as a study from the Cleveland Clinic that found each successive vaccine dose increased the risk of infection.
Other papers have also estimated that protection against infection turns negative over time. Some datasets have indicated that vaccinated people were at higher risk of hospitalization, long seen as a surrogate for severe disease.
Researchers in one recent paper said that repeated vaccination—some Americans have received a half-dozen COVID-19 shots in under three years—weakens immune systems, potentially making people susceptible to life-threatening conditions such as cancer.
The estimates were negative even after CDC officials made adjustments for factors such as age, sex, and ethnicity. The median time since the last dose for the people who only received one or more doses of an old vaccine was 464 days. For the group who received a bivalent vaccine but saw effectiveness turn negative, the median time was 137 days….