Second dose with different vaccine? Early Studies: Much More Effective. Benefits and Risks

Second dose with different vaccine? Early Studies: Much More Effective. Benefits and Risks
Second dose with different vaccine? Early Studies: Much More Effective. Benefits and Risks

Make the second vaccination with a different vaccine from that inoculated in the before? There is one i study spanish published in recent weeks on the magazine “Nature“which would testify to the effectiveness of this system. Other trials have started and many immunologists have already expressed their support. And in the world there are already countries like Canada who authorized this practice.

“The vaccination of people with both vaccines Oxford-AstraZeneca e Pfizer-BioNTech COVID-19 produce una powerful immune response against the SARS-CoV-2 virus, “suspected Spanish scientists conducting the Combivacs study.

“It seems that the Pfize vacciner significantly enhanced antibody responses in single-dose AstraZeneca vaccinees. This is wonderful news, “he says Zhou Xing, immunologist at McMaster University in Hamilton, in Canada, a country that has already decided to embrace this strategy. Xing even claimed that Pfizer’s antibody response to boost it seems to be even stronger than that generated by most people after receiving two doses of the Oxford-AstraZeneca vaccine, according to data from previous studies.

“Starting in April, the Spanish study CombivacS has enlisted 663 people who had already received a first dose of the vaccine Oxford-AstraZeneca, which uses a harmless chimpanzee ‘adenovirus’ to instruct cells to make a SARS-CoV-2 protein. Two-thirds of the participants were randomly chosen to receive the vaccine based on mRNA manufactured by Pfizer, based in New York, and BioNTech, in Mainz, Germany, at least eight weeks after the first dose. A control group of 232 people have not yet received a recall. The study was conducted byCarlos III Health Institute of Madrid“, we read in” Nature “.

Combivacs enrolled 663 participants aged 18 to 59 who had already received a dose of AstraZeneca: those who received a second dose of the Pfizer vaccine, 450 subjects, showed an increase in 150 times the antibody titers, which remained evident 7 days after administration. However, the same authors point out that more data from larger studies are needed to confirm immune responses.

Another study whose preliminary data have just been published in Lancet – the English research called Com-COV on 830 subjects over-50 – has instead shown that the mix with a first dose of AstraZeneca and the second with Pfizer determines a increased mild adverse reactions come fever, fatigue, headache and paini, with “some short-term disadvantages” that can be mitigated with the use of paracetamol. Such side effects were reported in 34% of the sample, compared to 1.7% found in the Spanish study.

Daniel Altmann, immunologist at Imperial College London explained that: “Una strong immune response the mix-and-match strategy is “entirely predictable from basic immunology“.

Immunology also questions the future. In the case of the third dose. In this situation adenoviruses would lose progressively their effectiveness. “Repeated doses of virus-based vaccines like that of Oxford-AstraZeneca tend to be less and less effectivei, because the immune system mounts a response against adenovirus. RNA vaccines, on the other hand, tend to trigger stronger side effects with additional doses. “I think there is a brave new world of vaccinology to be considered in all of this, “Altmann told Nature magazine.

To the US National Institute of Health (Nih) a new research has just started in this sense: su 150 fully immunized volunteers, who had received one of three US approved vaccines – J&J, Moderna or Pfizer – a different brand booster will be tested. A note from the Nih makes it known that the first objective of the investigation will be to verify the safety and immune potency of the new regime. THE participants will be followed for a whole year but the first results should be achieved by the end of the summer. In South Korea A trial has already started on the alternate use of one of the following vaccines: AstraZeneca, Moderna or Pfizer. China is also progressing with studies of an alternation of anti-covid vaccines developed in the country. And just these days, similar tests will begin in Great Britain in which the use of a different vaccine will be experimented with respect to the first two doses already administered, specifically for a subsequent booster.

Also in Italy, at the Spallanzani Institute in Rome, a trial on the second dose started last April, after the first with AstraZeneca, using other vaccines including lo Sputnik.

From the beginning of June in Canada it is possible to receive a second dose of a vaccine against Covid-19 different from the one that was given as the first dose. And the decision of the Ottawa Public Health Agency following the new guidelines issued last Monday by National Commission of Immunization Consultants. In detail, those who have received a first dose of the AstraZeneca vaccine will be able to receive a second dose of one of the two messenger RNA vaccines, Pfizer / BioNTech or Moderna. Anyone who has received a first dose of Pfizer/BioNTech may receive a second dose of Moderna and vice versa. Theresa Tam, Canadian public health number one, explained that it remains “optimal” to receive two doses of the same vaccine. However, this is not always possible due to the supply problems that Canada is experiencing, in particular as regards Modern and AstraZeneca.

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