Mix-vaccination with AstraZenaca and Pfizer COVID-19 vaccines is Safe?

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Mix-vaccination with AstraZenaca and Pfizer COVID-19 vaccines is Safe?

Mix-vaccination with AstraZenaca and Pfizer COVID-19 vaccines is Safe? Let’s understand “Enhanced” immune response first!

Two different types of vaccines have been vaccinated successively, called Heterologous Prime Boost (heterologous prime boost). The first shot is “primary immunization” and the second shot is “boosted immunization”. The purpose is to stimulate more intense Heterologous means that different types of vaccines are used before and after.

In previous research on Ebola virus vaccines, the Shanghai Pasteur Institute of the Chinese Academy of Sciences adopted this approach. In August 2017, the Pasteur Institute issued a document stating that the chimpanzee adenovirus type 7 (AdC7-GP) was used as the primary vaccine, and the GP1 recombinant protein (GP1t) with the transmembrane region removed was prepared by genetic engineering as a booster vaccine. It was found that the antibody titer and durability were significantly better than homologous primary immunization-enhancement, and the serum neutralizing antibody remained at a high level 18 weeks after immunization.

UK: Mix vaccination by AstraZeneca and Pfizer vaccines

On February 4, 2021, the United Kingdom launched a clinical trial similar to CombivacS. Subjects are 50 years of age and above, and the AstraZeneca adenovirus vector vaccine (ChAd) was “mixed” in a two-dose course of treatment. With Pfizer’s mRNA vaccine (BNT), to evaluate whether it will cause an “enhanced” immune response and whether it can fight against mutant viruses.

On May 19, the “Lancet” released the results of this clinical trial: the heterologous vaccination program produced greater systemic reactogenicity than the homologous vaccination after the “boost immunization”.

Clinical data shows:

Among those vaccinated with ChAd followed by BNT combination, 34% (37 cases/110 cases) developed fever symptoms, and among those who were vaccinated with two injections of ChAd, this data was 10% (11 cases/112 cases).
Among those vaccinated with BNT followed by ChAd combination, 41% (47 cases/114 cases) developed fever; and among those who received two injections of BNT, this data was 21% (24 cases/112 cases).
In addition, in the heterologous vaccination group, adverse reactions such as chills, fatigue, headache, arthralgia, and muscle aches were also increased compared to homologous vaccination, and most of them occurred within 48 hours after vaccination, but there were also no patients who needed it. Hospitalized for treatment.

The paper pointed out, “It is particularly noteworthy that these data were obtained in subjects over 50 years old, and in younger people, the reactogenicity may be higher.”

However, the original intentions of the two trials are slightly different. Raquel Yotti, director of the Carlos III Health Institute, mentioned in an interview that the purpose of the CombivacS trial is also to find people who have received the first dose of AstraZeneca’s adenovirus vector vaccine. Subsequent alternative vaccination programs. “

It is reported that the CombivacS trial was started after the AstraZeneca vaccine was discontinued in people under 60. At the beginning of March, AstraZeneca vaccine was caught in a “thrombotic storm”. Due to the successive occurrence of adverse reaction reports, the Philippines, South Korea, Austria, Denmark, Norway, Iceland, Spain… Many countries around the world announced the suspension of AstraZeneca vaccination.

According to the report, the results of the CombivacS trial initially proved the feasibility of vaccination against the heterologous new coronavirus.

At present, many European countries including Germany, France, Sweden, Norway and others who have been vaccinated with AstraZeneca adenovirus vector vaccines under the age of 60 have suggested considering subsequent heterologous vaccination, but there are still many countries / The region is still further analyzing its scientific basis and safety.

In addition, according to a report by Agence France-Presse in London on May 19, the British government launched a clinical trial on the third dose of the COVID-19 vaccine that triggered an immune response. The National Health Agency of the United Kingdom initiated 2886 people who completed two doses of the vaccine. The vaccinated volunteers will participate, and the study will observe seven vaccines from companies such as AstraZeneca, Pfizer, and Moderna.

According to reports, the British government intends to rely on large-scale testing and accelerated vaccination to curb the spread of mutant viruses. At present, 70% of British adults have received the first dose of the vaccine, and 40% have completed the two doses.

Spain: Data reveals the effects and side effects of mix-vaccination

According to “Nature” reports, on May 18, the results of a Spanish clinical trial called CombivacS showed that after being vaccinated with AstraZeneca’s adenovirus vector vaccine and Pfizer’s mRNA vaccine, participants produced higher levels of antibodies , And these antibodies can identify and inactivate the new coronavirus in laboratory tests. In the control group that was not vaccinated with the second dose of mRNA vaccine, the antibody levels of the participants did not change significantly.

Researchers of the project said that people under 60 who have already received a dose of AstraZeneca vaccine can safely use Pfizer’s mRNA vaccine as a second dose of vaccination, which can not only trigger a stronger immune response, but also effectively relieve it. This solves the problem of vaccine supply fluctuations faced by some countries.

The trial was initiated by the Carlos III Health Institute in Madrid, Spain. A total of 663 volunteers were selected, all of whom had received a dose of AstraZeneca adenovirus vector vaccine 8-12 weeks ago.

Participants were divided into two groups. 442 people received the second dose of the mRNA vaccine, and 221 people served as a control group and did not continue to receive any other vaccines.

Mix-vaccination with AstraZenaca and Pfizer COVID-19 vaccines is Safe?
1.7% of participants reported significant side effects

The results showed that 14 days later, the IgG antibody level in the blood of the people who received the second dose of the mRNA vaccine was 30 to 40 times higher than that of the control group who received only one dose of the vaccine. After the second vaccination, the antibody titer of the two-dose “mixed” vaccine group increased by 120 times a week, and reached 150 times after 14 days, while the control group remained at the same level as when the experiment started.

In the evaluation based on antibody efficacy, the testers mixed the patient’s serum with coronavirus samples in the laboratory and found that the neutralizing antibody titer was 7 times higher than before, even better than other similar vaccination data.

The population who received only one dose of adenovirus vector vaccine was selected as the control group of adenovirus vaccine plus mRNA vaccine booster, which is derived from some past experience in the immune characteristics of adenovirus vaccine. According to Daniel Altmann, an immunologist at Imperial College London, repeated doses of adenovirus vector vaccines tend to be less effective because the body’s immune system also responds to adenoviruses. In contrast, mRNA vaccines may have stronger side effects when the dose is increased.

In addition, the person in charge of the CombivacS trial said that in this clinical trial, only 1.7% of the participants reported significant side effects, but only for headaches and muscle pain, and no one was hospitalized for this.

According to the conclusion of the Carlos III Institute of Health, it is “highly immunogenic and safe” to continue to inject the second dose of mRNA vaccine after vaccination with adenovirus vector vaccine.

China CDC: Most COVID-19 vaccines are inactivated vaccine

On May 20th, Shao Yiming, a researcher of the Chinese Center for Disease Control and Prevention and a member of the Vaccine R&D Expert Team of the Scientific Research Group, stated at the State Council’s Joint Prevention and Control Press Conference that the effects of vaccines using the same technical route from different manufacturers are exactly the same. Will not affect the safety of the vaccine.

“And some research data seen in the world shows that vaccines of different technical routes are also being’mixed’, in order to induce a stronger and longer-lasting immune response.” Shao Yiming said, “but there is no medicine yet. The supervisory department reviewed and determined that it is a new immunization strategy, which is in the stage of data accumulation. We have been paying attention to it, including some countries, which is also conducting research in this area.

In fact, the vaccine mix and match of different technical routes, internationally, relevant research data is also being published, but the vaccines involved in these studies are mostly adenovirus vector vaccines and mRNA vaccines, the mainstream species inoculated in China-inactivated vaccines , Hardly involved.