Reinforcement of Covid vaccine against omicron variant bar, study suggests

Even the three doses of mRNA vaccines against Covid did not prevent infection by the omicron variant, according to a South African study published on Thursday (9). The work is in pre-print form, yet without peer review.

The research examined the effects of three doses of immunizers such as Pfizer/BioNTech or Moderna, plus one dose of Oxford/AstraZeneca vaccine and two doses of Pfizer.

These real-world records (that is, they are not laboratory tests) suggest that omicron can cause infections in individuals who have already received booster doses.

The result contradicts the announcement made by BioNTech and Pfizer on Wednesday (8). The companies said that three doses of its immunizing agent are effective against omicron, but the finding came from laboratory testing. On the same day, the WHO said that it was still not possible to say whether the booster doses could prevent infection with the new variant of the coronavirus.

In the South African study, researchers investigated seven patients who traveled from Germany to Cape Town, South Africa. The subjects’ average age was 27.7 years.

Among them, 6 had received primary vaccination from Pfizer/BioNTech, of which 5 had received a booster from the same immunizer, and 1 from Moderna. The seventh patient received the first dose from Oxford/AstraZeneca and the two subsequent doses from Pfizer/BioNTech. All booster doses were applied in October and November and none of them reported previous coronavirus infection.

Upon arrival in the country, all patients had tested negative for Sars-CoV-2. After a few days, they reported flu-like symptoms, underwent a test and were kept in isolation.

During the study period, patients were instructed to record their symptoms in a diary. At the end of the observation period, all reported dry cough, most reported allergic rhinitis (71.4%) and sore throat (57.1%), and some mentioned shortness of breath (42.9%). There was also mention of fever (14.3%), fatigue (71.4%) and headache (57.14%), but only in the first days of infection. No case was considered serious.

Genomic sequencing of the samples identified the omicron variant in 5 of the 7 patients. In 2 of them the result was inconclusive; however, given the similarity between the symptoms and the epidemiological moment, when the country had a high incidence of new cases of Covid, the researchers believe that the strain was also responsible.

To assess the rate of anti-spike antibodies, that is, capable of neutralizing the S protein of the virus and preventing its entry into cells, the authors collected serological samples from those infected and found an average rate of 23 thousand units per milliliter, which approximates that observed after the second dose of the vaccine, but less than that found with the third dose.

The data found indicate the probability that the omicron variant will manage to escape neutralizing antibodies even after a third dose of the vaccine. The study authors emphasize the importance of maintaining non-pharmacological protective measures, such as the use of masks and physical distance, to prevent infections by the new strain, even in individuals vaccinated with three doses.

In general, Covid vaccines were developed to protect especially against hospitalization and death, but they do not have the power to completely contain the contagion itself. Thus, even vaccinated people can contract the virus and become ill, so it is important to continue using masks after immunization.

The so-called vaccine escapes can occur, but their frequency in the population and the seriousness of the cases still need more time to be investigated.

The authors also point out that most South Africans still do not have booster doses available. Across the African continent, 10% of the population received at least one dose of vaccines against Covid, a number that drops to 7% when considering the two doses, until the last 8th of December.

The inequality between the countries of the continent is also great, with Tunisia, for example, in the north of the continent with 52% of the population with at least one dose and 44% with two doses, but Nigeria with less than 2% of the population with at least one dose.

Low vaccination coverage is a problem both in terms of availability of doses, since rich countries have made massive purchases of vaccines, and in terms of the logistics to apply immunization agents, with the lack of health professionals and syringes.