The ability of the COVID-19 vaccines to prevent severe illness and hospitalization wanes over time, a CDC study finds.
Researchers at the agency found that the effectiveness of severe illness prevention drops from as high as 89 percent to as low as 75 percent 120 days after the second shot of the Moderna or Pfizer-BioNTech vaccine is received.
The data was gathered by the agency from February to September, though, meaning the Omicron variant had not yet been discovered at the time.
Still, the CDC researchers say that these data show the need for Covid booster shots, especially among people who are more vulnerable to the virus.
More recent data also finds that the initial two-shot vaccine regimen is not as effective against the new Omicron variant.
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
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
The CDC researchers gathered data from 1,900 fully vaccinated veteran patients at five Veterans Affairs hospitals around the country.
They followed the group, which included people of all ages 18 and older, from February to September 2021.
Study participants who had received the Moderna vaccine where found to have higher antibody levels than those who received the Pfizer-BioNTech vaccine within the weeks following vaccination.
The research team found that, after gathering hospitalization data among participants and adjusting for age and risk factors, the Moderna shot reduced risk of hospitalization from Covid by 89.6 percent.
Pfizer vaccine recipients had their risk of hospitalization dropped by 86 percent.
Researchers continued to gather samples and test antibody levels through out the study period.
They found that, over the first four months after receiving vaccination, antibody levels would wane.
‘Among recipients of Moderna and Pfizer-BioNTech vaccines, anti-SARS-CoV-2 spike and RBD IgG levels declined with increasing time since vaccination,’ researchers wrote.
‘Although U.S. veterans who received the Moderna vaccine consistently had higher antibody levels compared with recipients of the Pfizer-BioNTech vaccine across age groups and time since vaccination.’
After four months, the antibody levels of people who had received the vaccine had fallen, and the shots’ effectiveness are preventing hospitalization also dropped over time.
The researchers found that after 120 days, effectiveness of the Pfizer vaccine at preventing hospitalization dropped all the way to 75.1 percent.
For Moderna recipients, effectiveness against hospitalization fell slightly to around 86 percent.
‘Although an immune correlate of protection for COVID-19 vaccination has yet to be established, studies have shown a relationship between binding antibody levels, neutralizing antibody levels, and vaccine efficacy in clinical trials,’ researchers wrote.
This study was performed before the Omicron variant was discovered last month, and information that has been revealed about the virus strain since has only solidified the need for boosters.
Data revealed Tuesday night by the African Health Research Institute found that people fully vaccinated with the Pfizer vaccine do not have the same level of protection against Omicron that they have against other virus strains.
On Wednesday, the company said it had data showing people who had only received the first two shots were not as immune to the new strain, but that a booster shot would increase antibody levels 25-fold.
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.
The Food and Drug Administration expanded eligibility of the Pfizer booster shots on Thursday, allowing 16 and 17 year old Americans to get the additional vaccine dose.
According to official CDC data, 49 million Americans have received the additional Covid shot, with around half of them opting to receive the Pfizer booster.