A new study from the U.S. Centers for Disease Control and Prevention (CDC) has shown that protection against severe COVID-19 illness begins to wane four months after receiving the booster (third) dose of mRNA vaccines, according to World Pharma News.
Until this study, experts did not know about the durability of protection after the third dose, especially during the Delta and Omicron waves in the U.S.
The study’s co-author Dr. Brian Dixon said, “The mRNA vaccines, including the booster shot, are very effective, but effectiveness declines over time. Our findings suggest that additional doses may be necessary to maintain protection against COVID-19, especially for high-risk populations.”
“We also found that people who are Hispanic or Black are half as likely to have a third vaccine dose than people who are white, making people who are Hispanic or Black more vulnerable to severe COVID and highlighting the need for public health officials to double down on efforts to protect these vulnerable populations,” he added.
Dr. Dixon is the director of Public Health Informatics, Regenstrief Institute, Inc., and Indiana University Richard M. Fairbanks School of Public Health.
The CDC study reported that those who took second and third doses of an mRNA vaccine (Pfizer or Moderna) had greater protection against hospitalizations than against emergency room (ER) or urgent care (UC) visits. Also, the study found that the efficacy of mRNA vaccines was lower during the Omicron wave than during the Delta wave.
Vaccine effectiveness against ER or UC visits declined from 97% within the first two months of receiving a booster shot to 89% effectiveness at four months during the Delta period. And during the Omicron period, the efficacy against ER or UC visits decreased from 87% during the first two months after receiving the third dose to 66% at four months after a booster dose.
After the booster dose, immune protection against Delta-associated hospitalization declined from 96% within two months to 76% after four months. For Omicron, immune protection decreased from 91% during the first two months to 78% at four months.
Another co-author Dr. Shaun Grannis said, “Our findings confirm the importance of receiving a third dose of mRNA COVID-19 vaccine to prevent moderate-to-severe COVID-19 illness, especially among those with comorbidities. That protection conferred by mRNA vaccines waned in the months following a third vaccine dose supports further consideration of booster doses to sustain protection against moderate-to-severe COVID-19 illness.”
