The study shows the declining efficacy of the third dose of mRNA vaccines

A new study shows that resistance to severe COVID-19 begins to wane 4 months after receiving the third dose of mRNA vaccine. A decay of immunity was observed during both Delta and Omicron variants waves. Although similar to the second dose, protection decreased over time after the third dose, the third dose was still very effective in preventing severe COVID-19 disease.

"mRNA vaccines, including boosters, are very effective, but their effectiveness declines over time. Our finding suggests that additional doses may be needed to maintain protection against COVID-19, especially in high-risk populations, said study co-author Dr. Brian Dixon, director of public health informatics at Indiana University Richard M. Fairbanks School of Public Health. .

The study also found that vaccine efficacy was generally lower with the Omicron variant than with the Delta variant dominance, but at the same time, the study results clearly showed that those who received the second and third doses of the vaccine mRNA, had greater protection against the severe course of the disease and the need for hospitalization.

The efficacy of the vaccine in preventing severe disease (requiring an emergency room visit) fell from 97% in the first two months following a booster dose to 89% success after four or more months in dominance of the Delta variant (summer/early fall 2021). During the dominance of the Omicron variant (late fall 2021/winter 2021-22), vaccine efficacy in preventing severe disease was 87% in the first two months after the third dose, dropping to 66% after four months after the third dose.

After the third dose, the protection against hospitalization associated with the Delta variant fell from 96% in two months to 76% after four months. Vaccine efficacy against the severe disease associated with the Omicron variant was 91% in the first two months, and fell to 78% in four months.

The US Centers for Disease Control and Prevention collaborated with six US healthcare systems and the Regenstrief Institute to create the VISION network to evaluate the effectiveness of the COVID-19 vaccine. Columbia University Irving Medical Center, HealthPartners, Intermountain Healthcare, Kaiser Permanente Northern California, Kaiser Permanente Northwest and the University of Colorado are also members of the network.

Source: ScienceDaily