Effectiveness Decreases after 4 Months, Booster Vaccine Is Still Needed


The effectiveness of the third dose of Pfizer and Moderna mRNA booster vaccines is said to be substantially reduced after 4 months. Recent research published by the United States Centers for Disease Control and Prevention (CDC) examined the level of protection of the COVID-19 booster vaccine against the Omicron variant.

Even so, they believe that the injection of the Pfizer booster vaccine is still able to reduce the risk of hospitalization due to infection with the Omicron variant.

This conclusion was drawn from the CDC’s Morbidity and Mortality Weekly Report study which explored the effectiveness of the COVID-19 vaccine in reducing the risk of hospitalization of COVID-19 patients and emergency care. They compared adults in the US who had already received two doses with three doses of the COVID-19 vaccine.

The data includes 241,204 emergency department or emergency care visits and 93,408 hospitalizations in 10 states, as of August 26, 2021, and January 22, 2022.

Vaccine efficacy was estimated by comparing the likelihood of a positive Covid test between vaccinated and unvaccinated patients and using statistical methods to control for a calendar week, geographic region, while adjusting for age, local transmission rate, and patient characteristics such as comorbidities.

Protection faded further in preventing emergency care, dropping from 87 percent in the first two months to 66 percent after four months.

The vaccine’s efficacy against hospitalization was 91 percent in the first two months but dropped to 78 percent in the fourth month after the third dose. After more than five months, the vaccine’s effectiveness had dropped to about 31 percent, but the researchers noted that the estimate was “inaccurate because there is little data available” for that group of people.

The researchers found booster shots remained highly effective against moderate and severe COVID-19 for about two months after the third dose. But its effectiveness decreased substantially after four months, indicating the need for an additional boost, the study said.

“The finding that the protection afforded by the mRNA vaccine diminishes within months of receiving the third vaccine dose reinforces the importance of further consideration of additional doses to maintain or increase protection,” concludes the authors.

Protection from the two-dose vaccine regimen has decreased since omicron became dominant, but a third dose boosts the immune system back to strong levels to prevent moderately severe disease, a previous CDC study found.

Diminished immunity after the third injection of the mRNA vaccine during omicron has been observed in Israel and a preliminary report from the CDC, the study said. But Friday’s report represents the first real-world data in the United States on the durability of that protection over deltas and omicrons.

In a statement, the CDC said boosters are “safe and effective” and research shows that the third dose of mRNA vaccine “continues to offer a high level of protection against severe disease, even months after administration, underscoring the importance of staying up-to-date when eligible after receiving it. main series.”