Europe Endorses Mixing & Matching COVID-19 Vaccines

The European region is currently experiencing a rising number of SARS-CoV-2 virus infections in the ongoing COVID-19 pandemic and an increase in hospitalization rates.

Unfortunately, only 66.4% of Europeans are fully-vaccinated as of December 7, 2021.

In response, the European Medicines Agency (EMA) and the European Centre for Disease Prevention and Control (ECDC) urge EU citizens to adhere to recent recommendations on COVID-19 booster vaccination.

In line with measures already taken by many EU Member States, an increasing number of clinical studies, supported by real-world evidence, have now looked at the possibility of using two different COVID-19 vaccines.

Either for the first and second doses of an initial course, known as heterologous primary vaccination, or using a third dose of a different COVID-19 vaccine as a heterologous booster.

The heterologous regimens have been found generally well tolerated.

The EMA and ECDC have recently published technical recommendations and advice on heterologous vaccination against COVID-19, either in the primary course or as a booster.

Evidence from studies on heterologous vaccination suggests that the combination of viral vector vaccines and mRNA vaccines produces good levels of antibodies against the SARS-CoV-2 virus and a higher T-cell response than using the same vaccine (homologous vaccination) whether in a primary or booster regimen. 

The use of a viral vector vaccine as the second dose in primary vaccination schemes, or the use of two different mRNA vaccines, is less well studied.

While research is ongoing to provide more evidence on long-term safety, duration of immunity, and effectiveness, the use of heterologous schedules may offer flexibility in terms of vaccination options, mainly to reduce the impact on the vaccine rollout should a vaccine not be available for any reason.

Although the EMA - ECDC review did not look at other vaccines not yet licensed in the EU, such as Sputnik V, research into heterologous combinations of these will be considered in the future as more evidence becomes available.

There are four vaccines currently authorized in the EU; the two mRNA vaccines Comirnaty and Spikevax, and the adenoviral vector vaccines Vaxzevria and COVID-19 Vaccine Janssen (J&J).

The first 3 require a two-dose course, and Janssen is currently authorized as a single dose.

The EMA and ECDC re-emphasize the need to ensure that as many people as possible are fully vaccinated against COVID-19. In addition, there is an urgent need to close immunity gaps across Europe.

PrecisionVaccinations publishes fact-checked research-based vaccine news.