Pfizer and Moderna vaccines can lead to false positives for covid-19

In a considerable percentage of people immunized with Pfizer-BioNTech and Moderna, who target the protein spike SARS-CoV-2, an increase in antibodies capable of recognizing a fragment of another viral protein (the N protein) It ends like this a study of the Global Health Institute of Barcelona (ISGlobal), a center promoted by the “la Caixa” Foundation, which has implications for the detection of infections in vaccinated people.

All guidelines approved for use in Europe use as antigen the protein spike SARS-CoV-2 and consequently induce the production of antibodies directed against this protein. To find out if a vaccinated person has been infected, antibodies are measured against others viral proteins not included in the injection, such as protein N.

“With the appearance of new variants with the potential to evade immunity, it is especially important to be able to measure the number of vaccinated people who have been infected,” he explains. Carlota Dobaño, first author of the study.

an unexpected find

Since the beginning of the pandemic, Dobaño and his team have closely followed the production and duration of antibodies against different viral antigens in two cohorts of healthcare professionals in Catalonia (SeroCov and CoviCatCentral). In this study, carried out in collaboration with the Catalan Institute of Health of Central Catalonia, describe a unexpected find: vaccines MRNA (Pfizer-BioNTech or Moderna) induce the production of antibodies that not only recognize the protein spike, but also a region of the N protein. SARS-CoV-2

The team noted that, after vaccination, there was a significant increase in IgG antibodies able to recognize the Fragment C terminal of protein N in a considerable percentage of cases (in 36% of people who received the injection of Modern, and 13% who received the to do) Moderna’s vaccine also induced an increase in antibodies capable of recognizing the entire N protein, although in a smaller percentage.

“This phenomenon does not seem to be the result of a reactivation of immunity previously acquired by an infection, as it was observed both in people with the previous disease and in those who had not been infected”, he indicates. Gemma Moncunill, author of the study.

O hypothesis most likely vaccination with spike can induce antibodies with cross-reactivity towards the C-terminal fragment of the N protein.

To detect vaccine failures, it is best to use multiple antigens

These results are relevant in public health, since the use of protein N to detect infections in vaccinated people has been proposed. “This could result in an overestimation of vaccine failures, as a considerable percentage of cases would be falsely classified as asymptomatic infections,” emphasizes Dobaño. In consequence, The efficiency of the vaccine against infections.

The authors conclude that the N protein (or in any case, the C-terminal fragment) is not a good candidate for detecting vaccine failures, and that it is better to use a combination of multiple viral antigens. This will allow for a better assessment of the effectiveness of vaccines.

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