Covid News: Study shows that booster shots wane after four months, more shots may be necessary.

In a study conducted by the United States' Centers for Disease Control and Prevention (CDC), it was found that the efficacy of the booster shots of Pfizer and Moderna waned quite significantly up to the four (4) month mark. The findings were announced by the agency on Friday, February 11, 2022.

Though it was a known fact that efficacy for the two mRNA vaccines weakens and diminishes up to four to six month after two doses, very little research had gone into studying the impact a booster or third shot would have on building immunity against COVID-19, until now. 

The CDC revealed that the new study was based on records of patients' visits to emergency departments, urgent care clinics and hospitalisations. The CDC monitored data from the period August 26, 2021 to January 22, 2022. During that time there were more than 241,204 cases of visits to the emergency department or an urgent care clinic, and 93,408 hospitalisations, which are more serious, among adults with COVID-19–like illness.

Vaccine efficacy was estimated by comparing the odds of a positive COVID test between vaccinated and unvaccinated patients and using statistical methods to control for calendar week, geographic area, while adjusting for age, the level of local transmission, and patient characteristics like comorbidities.

During the Omicron-predominant period, vaccine efficacy against COVID-associated emergency department or urgent care visits was 87 per cent during the first two months after a third dose, but fell to 66 per cent by the fourth month.

Vaccine efficacy against hospitalisation was 91 per cent in the first two months, but fell to 78 per cent by the fourth month after a third dose.

"The finding that protection conferred by mRNA vaccines waned in the months after receipt of a third vaccine dose reinforces the importance of further consideration of additional doses to sustain or improve protection," the CDC authors said. 

Speaking at a White House COVID briefing on Wednesday, President Joe Biden's top medical advisor Anthony Fauci said it was likely that fourth doses would more than likely be needed for subsets of people who mount weaker immune responses, such as the elderly and immunocompromised.

Meanwhile on Friday, the Food and Drug Administration (FDA) authorised a new lab-grown antibody treatment by pharmaceutical company Lilly called bebtelovimab.

The drug is administered as an intravenous injection over at least 30 seconds and has been green lighted for the treatment of mild-to-moderate COVID illness among people 12 and over at high risk of severe disease. 

Justification for the treatments' authorisation came from a clinical trial that showed the drug has strong promise against Omicron. Lilly's previous antibody treatment was de-authorised by the FDA after it was found to be ineffective against this variant.