A Covid-19 breakthrough infection is an infection in a fully vaccinated person 14 or more days after receiving the jab (CDC).
There have been reports of Covid-19 breakthrough infections amongst fully vaccinated people against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has raised more criticism from the anti-vaxxers who have wondered why would a vaccinated person get the virus again. A new study has, however, highlighted why a few of these people become re-infected. And the answer lies in the peak of neutralising antibodies following vaccination. We explain the phenomenon in today’s article.
Bergwerk M et al. identified and evaluated Covid-19 breakthrough infections among fully vaccinated health care workers at a medical centre in Israel. They identified 39 breakthrough infections out of 1497 fully vaccinated workers. They noted that these patients had lower peri-infection neutralising antibodies compared to the matched normal counterparts. Furthermore, they observed that those who had higher levels of neutralising antibodies within the peri-infection period were less likely to be infectious. Most of the patients had mild symptoms, and 85% had the alpha variant isolated. On further analysis, they observed that the patients who had breakthrough infections following exposure were most likely to have had lower peak levels of the neutralising antibodies following vaccination than their normal counterparts.
A neutralising antibody is an antibody that defends a body cell from an infectious organism like a virus, bacteria by neutralising any biological effect it has. They are part of the adaptive immunity against viruses, bacteria, and toxins. Vaccines induce the formation of neutralising antibodies by the B cells (B lymphocytes). Some B cells (memory) retain the ability to continue producing neutralising antibodies against a particular organism, say SARS-CoV-2, such that protection against such continues for a prolonged period.
The study highlights that the peak levels of neutralising antibodies after vaccination may determine those who may suffer a breakthrough infection. Among those who get the breakthrough infection, high levels of neutralising antibodies a week before a diagnosis of Covid-19 may lead to low levels of infectivity. It’s noteworthy that even after vaccination, you will need to follow all the precautionary measures to limit exposure to SARS-CoV-2. It is because currently, we cannot measure your neutralising antibodies to determine whether you will likely get a breakthrough infection or not.
Download Bergwerk M et al. PDF from here.