Study: coronavirus vaccine series combining different preparations work as well as those in which the same preparation is used for each dose
According to a recent study, using different vaccine preparations in a series of coronavirus vaccinations works as well as when the same vaccine was used for each dose. The Finnish Institute for Health and Welfare (THL) studied the effectiveness of the coronavirus vaccines in cooperation with health officials from Denmark, Norway, and Sweden. The effectiveness of the vaccines was monitored after two and three doses.
“Vaccines have arrived in Finland at different times, which is why many have been administered several different types of vaccine. Our study indicates that a series of vaccines is equally effective in protecting against coronavirus infection or a severe case of coronavirus disease regardless of whether the same preparation or a combination of different preparations is administered. The possibility to administer whichever vaccine that has been available at the point of vaccination has led to improved vaccine coverage without compromising on the protection given by the vaccines”, says THL statistician Ulrike Baum.
One of the most common vaccine combinations in Finland has been two doses of AstraZeneca's Vaxzevria and one dose of the Pfizer Comirnaty vaccine. There was no difference in the risk of a coronavirus infection among those who were given this combination, and when the Comirnaty vaccine was used for all three doses. Furthermore, no differences were observed in cases of coronavirus disease requiring hospitalisation between the two different types of vaccination series. Nordic cooperation provided an extensive population base of 23 million people, making it possible to study the effects of rarer vaccine combinations as well.
The researchers also examined how much additional protection was provided by a third dose. Evaluating the effectiveness of a third dose showed that the effect was clearest against severe coronavirus disease. In Finland a third Comirnaty vaccine reduced the risk of hospitalisation by 78 percent and the risk of death by 88 percent compared with those who had been vaccinated only twice.
Children’s vaccinations prevent severe cases of coronavirus disease, but protection against infection is low
Denmark deviated from the other Nordic countries in the research period by recommending vaccinations for all children aged 5–11. The aim of this was to reduce the number of coronavirus infections among children and to reduce the spread of the virus in the rest of the population as well. The study nevertheless found only a small difference between vaccinated and unvaccinated children in the number of infections by the Omicron variant. The vaccination nevertheless provided good protection against infections that required hospitalisation.
“Existing coronavirus vaccines only slightly reduce the risk of infection by the Omicron variant. Based on our study, the risk of Danish children who had been vaccinated twice of being infected by coronavirus was about 9 percent lower than among the unvaccinated in the first three months after the vaccination. However, vaccination against coronavirus reduces the already very small risk of severe coronavirus disease by about 80–90 percent. Severe symptoms among both unvaccinated and vaccinated children were very rare especially in the Omicron period”, says Medical Specialist Eero Poukka at THL.
The study was funded by the European Medicines Agency (EMA). Data from the study is to be utilised in future recommendations for coronavirus for children and young people.
Further information
Eero Poukka
Medical Specialist
THL
[email protected]
Ulrike Baum
Statistician
THL
[email protected]
