For the third anti-Covid dose, only mRna vaccines are administered. Is there any benefit to combining them? Or vice versa, some problem? Is the booster more effective if Moderna and Pfizer are alternated? These are questions that many people ask themselves, especially in the impossibility of being able to choose the vaccine. “On the alternation of the two mRna vaccines there is no study that indicates an advantage, but not even a disadvantage: taking a third dose with Moderna after two with Pfizer and vice versa has no contraindications for either efficacy or safety”, he says. Roberto Tail, director of the Infectious Diseases Complex Operational Unit of the Gemelli Hospital in Rome. For this, the expert assures us, there is no problem in doing one or the other based on the availability of the vaccination center.
Covid vaccines, what is the third dose for?
by Aureliano Stingi
The anti-Covid vaccines Pfizer and Moderna have different characteristics, they are patented, but they are very similar because both have been developed on the basis of the ancestral viral strain of Wuhan and thanks to mRna technology they act on the Spike protein for the production of antibodies. .
“The lack of contraindications for efficacy and safety has also been underlined by the World Health Organization, both in the transition from adenoviral to DNA vaccine and within vaccines to mRna”, recalls the expert. After all, even DNA vaccines stimulate a response against Spike.
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According to some studies, there may even be an advantage when switching from the DNA-based adenoviral vector vaccine (which uses a virus that has lost its replicative capacity) like AstraZeneca and Johnson & Johnson to one-to-mRna like Pfizer and Moderna. . The so-called heterologous vaccination. There are examples in the scientific literature that show an improvement in the immune response. “The data are still open to confirmation but the mRna vaccine would stimulate the antibody-like response better, the adenovirus DNA one the cellular response. It could therefore be hypothesized that if a vaccine such as AstraZeneca and Johnson & Johnson is followed by an mRna one. you have a better protective response. This result needs further confirmation and should also be verified in the presence of variants “, explains the expert.
However, there are no studies to date that indicate a better or worse response in terms of efficacy by alternating the two mRna vaccines authorized in Europe. “They are very similar and I think the immune response is identical in quality and quantity,” Cauda repeats.
The effectiveness of the Pfizer double dose drops after a few months: an Israeli study says
by Giuliano Aluffi
“The point is that those who take three doses (regardless of the type of vaccine they use) have better protection against the disease. Against infection, we have seen, there is a decrease in efficacy over time. that even the third dose was less effective in protecting us in the presence of variants, a fourth dose with the updated vaccine may be needed. All this is obviously very preliminary, I do not find anything strange, we are in the presence of a pandemic, of something again “, concludes the expert.
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