Covid-19, changing vaccine for the second dose could increase mild side effects

Covid-19, changing vaccine for the second dose could increase mild side effects


Receiving the first dose of AstraZeneca vaccine and the second dose of Pfizer-BioNTech or vice versa could increase cases of mild post-vaccination side effects. But we are talking about known and common reactions, of reduced entity

(photo: Steve Buissinne via Pixabay) Changing vaccine at the booster with the second dose, therefore mixing vaccines based on different approaches, results to lead to an increase in vaccines that present mild and moderate side effects. This was stated by a group from the University of Oxford - a university that also developed the Vaxzevria vaccine, together with AstraZeneca - which today reports the first data of an ongoing study, called Com-Cov. The authors studied the following combination: a first dose with AstraZeneca's Vaxzevria and a second dose with Pfizer-BioNTech and vice versa. There is not yet a complete publication of the research, but the preliminary results are presented in a letter (peer reviewed) in The Lancet. The issue is also relevant because Germany and France have chosen to switch products for the administration of the second dose in people under 60 (in France under 55) who had received the first AstraZeneca vaccine - a hypothesis that is was also evaluated by other countries, including Italy.

The goal

The study started in February 2021 with the aim of understanding the safety and efficacy of a combined vaccination approach , so far not detailed. Such a scheme could be advantageous if the doses of a certain product are missing, due to supply problems or delays that, as we know, can occur in a pandemic. Furthermore, as the scientists explain in the letter published in The Lancet, it is important to study an approach that has already been chosen by some countries for those under 60 already vaccinated with AstraZeneca.

Therefore, Oxford researchers involved 830 participants and in the text they report the first data extrapolated from the study on safety and reactogenicity, or on the study of the reactions manifested following vaccination. To date, there are no investigations on this aspect in the case of combined vaccination schedules. The data on the reactogenicity of the trial are the symptoms reported by the patient himself, consulted by the researchers, both locally and systemically, in the 7 days following the reception of the first and second dose. In the study, participants received the second dose either 28 days or 84 days after the first, depending on the study group, in the trial they were in.

People with mild symptoms increase

Cases of fever, chills, fatigue, headache, joint and muscle pain and malaise increase in frequency. But there is no alarm. "The results of this study suggest that dose-mix vaccination schedules could result in an increase in days off work after immunization," said Mattew Snape, a lecturer in pediatrics and vaccinology at the University of Oxford, " and this is an important element to consider when planning the vaccination of healthcare professionals. To be stressed, there are no signs of safety concern and this result does not indicate whether the immune response is modified by the new approach. The authors hope to be able to answer this last question in the coming months. They are now evaluating whether early and regular use of paracetamol can reduce the frequency of these mild and moderate side effects.

Frame the case

After the very rare reports of abnormal thrombosis people under the age of 60, and potentially linked to the vaccines of the AstraZeneca and Johnson & Johnson houses, the scientists questioned how and when to administer the second dose of the vaccination in people under 60 who first received the AstraZeneca vaccine (recalling that Johnson & Johnson is single-dose). There are very few serious episodes, a few dozen out of millions of vaccinated people. Among the hypotheses discussed by the authorities, there was also that of providing the booster with a vaccine based on a different mechanism and the choice in that case would have fallen on Pfizer-BioNTech or Moderna messenger Rna (mRna) vaccines. After a careful evaluation, also based on the updated data of those who received the recall with AstraZeneca, the Italian Ministry of Health decided to administer the second dose as planned without changing anything.

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