Today, almost every second Swede (45 percent) over the age of 18 has received their third vaccine injection. It was clear early on that two doses of covid vaccine do not provide particularly good protection against being infected with omicron. However, double-vaccinated people are still protected against becoming seriously ill, needing hospital care or dying.
Several new studies now show that a third injection of mRNA vaccine (Pfizer-Biontech or Moderna) also seems to reduce the risk of infection and leads to a milder illness. Researchers in Qatar has examined how well a third booster dose protected against both infection and hospitalization among 2.2 million people in Qatar. Omikron is the dominant virus variant in Qatar, and the study lasted until the beginning of the year.
The study shows that the third syringe halves the risk of becoming infected and getting symptoms, compared to if you only took two syringes. It did not matter which vaccine was in the syringe, Modern or Pfizer-Biontech provided approximately the same protective effect.
– A third dose protects many against infection and thereby probably also contributes to reduced spread of infection. The result is perhaps expected, but still speaks its clear language: That it is worth taking the third dose, says Marcus Buggert, who is an associate professor of immunology at Karolinska Institutet.
The study from Qatar has not yet been reviewed and published in a scientific journal, and should therefore be interpreted with some caution.
Vaccinated in Sweden with three doses of vaccine against covid-19 by age group
Graphics: DN Source: Swedish Public Health Agency
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– It is good that studies are now beginning to show that three syringes really protect against omicrons. The new variant is considered “milder”, but we must not forget that it can still cause serious illness when many will be infected, says Marcus Buggert.
A British study in the medical journal The Lancet also recently showed a clear effect on the level of antibodies developed in the body after a third booster dose of Pfizer’s vaccine. Almost half (42 percent) of the study participants still had measurable levels of antibodies after two doses. About three weeks after the third dose, 96 percent of the participants had measurable levels.
The question is how long the vaccine protects against omicron. An American, yet unexamined laboratory study, shows that the protective effect against omicrons (measured at antibody level) remains for at least up to four months. Other preliminary results from studies among the population in both the USA, Great Britain and Israel show that the third booster dose protects against serious illness and hospitalization for at least three months.
Marcus Buggert believes that today we do not know how well three doses will protect against new virus variants.
– But it would surprise me if the vaccine would have no effect against future variants, he says.