Filenews 7 October 2021
A transient reduction over time in the immuno-protection of the Pfizer vaccine, while providing particularly high protection against severe disease, hospitalization and death, two new studies found.
The two studies conducted in Israel and Qatar and published in the Medical Journal of the New England Journal of Medicine, confirmed that immune protection remains high against severe disease, hospitalization and death, but their findings come to support the argument that even the fully vaccinated should be careful not to get infected with the coronavirus.
What the study in Israel showed for the Pfizer vaccine
The study in Israel analyzed data from 4,800 health workers, and it was found that antibody levels drop rapidly after two doses of the Pfizer vaccine "especially among men, people aged 65 and over and patients in immunosuppression." The researchers pointed out that the levels of so-called neutralizing antibodies – the first line of defence of the immune system against infection – are correlated with protection against infection, but for this study they studied only the levels of antibodies. "Published papers on many vaccines, such as those against measles, mumps and rubella, have shown a slight reduction each year from 5 to 10% in the levels of neutralizing antibodies. We found that months after vaccination there was a significant and rapid decrease in the chemical response to the BNT162b2 vaccine (of Pfizer/BioNTech)," dr. Gilli Regev Yohai and colleagues wrote.
The same study suggests that immunity lasts longer in people who have been vaccinated with the Pfizer/BioNTech formulation after having previously been infected with the coronavirus than in those who had made the two doses of the vaccine.
The study in Qatar
The second study conducted in Qatar focused on infections among the Gulf country's population with high vaccination rates. Citizens there were mainly vaccinated with the Pfizer/BioNTech formulation, also known as BNT162b2. "The protection provided through BNT162b2 against infection develops rapidly after the first dose, peaks in the first month after the second dose and then gradually weakens in the following months," noted Laith Abu Radad of Weill Cornell Medicine-Qatar and colleagues. "This decline seems to be accelerating after the fourth month, to reach a low level of about 20% in the coming months," they add, noting, however, that protection against the need for hospitalization and death remains above 90%.
The reduction in the protection of the Pfizer vaccine may be related to behaviour, they say. "Vaccinated individuals theoretically have more social contacts than unvaccinated people and may not comply so much with the protective measures. This behaviour may reduce the effectiveness of the vaccine in real-world conditions and possibly explain the reduction in protection," they write, warning of possible new outbreaks of the pandemic. "These findings suggest that a large proportion of the vaccinated population may lose its protection against infection in the coming months, potentially increasing the chances of new waves of the epidemic," they underline.
Pfizer argues that immunity from the first two doses of its vaccine begins to decline after a few months, and in September the U.S. Food and Drug Administration (FDA) approved the administration of booster doses some six months after the first two. The U.S. Centres for Disease Control and Prevention booster doses to the over-65s, to people with health problems that make them vulnerable, and to those at high risk of infection such as health workers and prison inmates. Israel is administering booster doses to its entire population and is now saying that it will require that those who want to be considered fully vaccinated have made three doses.
