Several European countries have already started giving booster doses.
The administration of a booster dose of the vaccine against covid-19 different from that received in the first injections can provoke, in some cases, a greater immune response, according to the European health authorities indicated on Tuesday.
The best results were obtained by first using a viral vector vaccine like that from AstraZeneca or Johnson & Johnson, followed by an injection of a messenger RNA (mRNA) vaccine like that from Pfizer and Moderna, they said.
The combination “can be used for both initial injections and boosters,” according to a joint statement from the European Medicines Agency (EMA) and the European Center for Disease Prevention and Control (ECDC).
It also allows countries to be more flexible when faced with a spike in infections, especially if stocks of a particular vaccine are depleted, they continued.
Several European countries have already started giving booster doses, six months after the initial COVID-19 injections, due to decreased immunity.
“The results of heterologous vaccination studies suggest that the combination of viral vector vaccines and mRNA produces good levels of antibodies (…) and a higher T-cell response than the use of the same vaccine,” explained the European health authorities. .
Antibodies are just one part of the immune response, which also involves cells called T cells. Although more difficult to measure, this “cellular immunity” plays a very important role, especially against severe forms of the disease.
Some studies suggest that side effects such as pain, fever, headaches and fatigue are higher after a combination of different vaccines, but the results are not “consistent,” the EMA and ECDC added.
So far, the European regulator has approved four adult vaccines in the European Union: messenger RNA vaccines from Pfizer-BioNTech and Moderna, and viral vector vaccines such as AstraZeneca or Johnson & Johnson.
According to the EMA and the ECDC, the rates of hospitalization and death from covid-19 are lower in the States of the European Union with the highest vaccination rates, regardless of the vaccines used. (I)
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