The European Union recommends “mix and match” vaccines in initial regimens and in booster doses. Especially if the first or the first two are viral vector vaccines, such as AstraZeneca and Janssen. This has been defended this Tuesday by the European Medicines Agency (EMA) and the European Center for Disease Prevention and Control (ECDC), which explain that an increasing number of clinical studies have examined the possibility of using two COVID- vaccines. 19 different doses, either for the first and second doses of a primary regimen (initial cycle), which is known as heterologous primary vaccination, or using a third dose of a different vaccine for the booster dose between 3 and 6 months after a primary vaccination cycle (heterologous booster).
Thus, the EMA and the ECDC explain that the data on heterologous vaccination “suggest that the combination of viral vector vaccines [tipo AstraZeneca] and mRNA vaccines [tipo Pfizer o Moderna] produces good levels of antibodies against the COVID-19 virus (SARS-CoV-2), as well as a higher T-cell response than using the same vaccine (homologous vaccination) either in the initial regimen or with the dose of reinforcement”.
“In general, the heterologous regimens were well tolerated”, state the EMA and the ECDC, which recalls that “the use of a viral vector vaccine [tipo AstraZeneca] as a second dose in the primary regimen, or the use of two mRNA vaccines [Pfizer y Moderna] different, it is less studied “.
“The data point towards an acceptable tolerability and boosted immune responses with the sequential heterologous vector vaccine[/ mRNA vaccine regimen versus the homologous vector vaccination regimen”, state the entities: “The heterologous regimen is capable of inducing an increase significant increase in immune responses, including enhanced memory B cells, compared to a homologous viral vector regimen. A slight increase in humoral immune responses is sometimes observed relative to homologous mRNA vaccination, but not consistently , generally supporting a similar antibody response. ”
The two EU bodies say that mixing and matching vaccines “can offer flexibility in the event that a vaccine is not available for whatever reason.”