A new peer-reviewed study found that the protection from Pfizer’s Covid-19 vaccine against the Omicron variant fades in just a week after receiving the second and third dose.
According to the Danish study published in JAMA Network on Friday, the researchers found a rapid decline in Omicron-specific serum neutralizing antibody titers only a few weeks after the second and third doses of Pfizer’s Covid-19 vaccine.
The study included 128 Danish adults that were vaccinated. Out of 128, 73 individuals received 2 doses of Pfizer vaccine and 55 received 3 doses of Pfizer (BNT162b2) between January 2021 and October 2021 or were previously infected prior to February 2021 and then vaccinated.
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Levels of omicron-specific “neutralizing” antibodies—which can target the virus and stop it from replicating—decline rapidly after a second and third dose of Pfizer’s shot, according to the Danish study of 128 people who had received two or three doses.
Antibody levels, which are associated with protection against infection and disease, fell within weeks of getting the shots and were much lower than the level of antibodies specific to the original and delta coronavirus variants, the researchers said.
Compared to original and delta variants, the proportion of omicron-specific antibodies detected in participants’ blood dropped “rapidly” from 76% four weeks after the second shot to 53% at weeks eight to 10 and 19% at weeks 12 to 14, the researchers found.
Omicron-specific antibody levels increased after the third dose—nearly 21-fold at week three and nearly 8-fold at week four, compared to four weeks after the second dose—and the shot generated a detectable response in most people for at least eight weeks, the researchers said.
However, antibody levels started to drop as early as three weeks after the booster shot, falling 4.9-fold for the original variant, 5.6-fold for delta and 5.4-fold for omicron between weeks three and eight.
You can read and download the study here.