A CDC study has shown that the COVID-19 vaccinations are less effective at preventing severe illnesses and hospitalization over time.

Research by the agency revealed that severity prevention effectiveness falls from as high at 89 percent to as low 75 percent after 120 days of receiving the Moderna vaccine or the Pfizer BioNTech vaccination.

Although the agency gathered the data from February to September of this year, it was still not possible to determine if the Omicron variant existed at that time. 

The CDC says that this data supports the use of Covid booster shot, particularly for those who are most at-risk.

Recent data shows that two shots of vaccine are not effective against Omicron.

A CDC research team found that antibody levels of people who received the Moderna of Pfizer COVID-19 vaccines slowly waned over time. They found that after four months, the Pfizer jab's (light blue) ability to prevent hospitalization had dropped to around 75%. The Moderna shot's (blue) effectiveness against hospitalization falls to 86% after four months

A CDC research team discovered that the antibody levels of Moderna of Pfizer COVID-19 patients slowly decreased over time. The Pfizer jab (light blue) effectiveness in preventing hospitalization dropped to 75% after just four months. Four months later, 86% of the Moderna (blue shot) effectiveness in preventing hospitalization has been lost

Researchers say the the study underscores the need for Covid booster shots, as people become more vulnerable to severe infection months after vaccination. The study was conducted before the Omicron variant was discovered - which is believed to be able to circumvent protection provided by the initial two-shot vaccine regimen. Pictured: An Army Sergeant in Fort Know, Kentucky, receives a shot of a COVID-19 vaccine on September 9

Researchers say that the results of the study highlight the importance of Covid booster shots as individuals are more susceptible to serious infection after vaccination. It was done before Omicron, which was believed to have the potential to override the two-shot initial vaccine regimen. Pictured: On September 9, an Army Sergeant from Fort Know (Kentucky) received a COVID-19 vaccination shot.

The CDC researchers gathered data on 1,900 veteran patients who were fully vaccinated in five Veterans Affairs hospitals throughout the United States.

From February 2021 to September 2021, they followed the group that included all people over 18 years old.

Participants who were vaccinated with the Moderna vaccine had higher levels of antibody than participants who were vaccinated with the Pfizer BioNTech vaccine in the following weeks.

Researchers found that Moderna had a lower risk of being hospitalized from Covid after analyzing the hospitalizations and adjusted for age and other risk factors.

Pfizer vaccination recipients saw their chance of being hospitalized drop by 86 per cent.

Through the course of their study period, researchers collected samples from participants and tested for antibody levels.

The researchers found that antibody levels declined over the four first months following vaccination.

Research found that anti SARS-CoV-2 antibody levels decreased with time after vaccination in Moderna and Pfizer BioNTech recipients.

“U.S. Veterans who had received the Moderna vaccine showed higher antibody levels than recipients of Pfizer BioNTech vaccines across age and time.

Four months after the vaccination, antibody levels had dropped and shots that prevent hospitalization have also decreased in effectiveness.

Researchers found that the effectiveness of Pfizer’s vaccine in preventing hospitalization fell to 75.1 percent after 120 days.

Moderna recipients had slightly less effectiveness in preventing hospitalization, falling to about 86 percent. 

Researchers wrote, “Although there is no immune correlate for COVID-19 vaccination, some studies have demonstrated a link between binding antibody levels, neutrizing antibody levels and vaccine efficacy during clinical trials.”

The study was done before Omicron variant of the virus was identified last month. Information that has since been made available about the virus strain has only strengthened the need to boost boosters.

According to data released by the African Health Research Institute Tuesday night, people who are fully vaccinated against Omicron have less protection than those who were vaccinated against other strains of the virus.

The company stated Wednesday that it has data showing that people who have received only the initial two doses of the vaccine are not as resistant to the second strain. However, a booster shot could increase the antibody level by 25 percent.

Moderna and Johnson & Johnson – the other two Covid vaccine manufacturers in the U.S. – have not revealed any information on the variant and their vaccines.

Thursday’s Food and Drug Administration expansion of eligibility for Pfizer booster shot allowed American 16-17 year-olds to obtain the added vaccine dose.

Official data from the CDC shows that 49 million Americans received additional Covid shots, and around half chose to get the Pfizer booster.