- Michelle Roberts
- Health Affairs Editor, BBC News Network
Image source,PA Media
A study in the United Kingdom found that inoculating the new coronavirus vaccine in a “mix and match” mode—that is, the first dose and the second dose of vaccines of different brands, can produce good protection against the new crown epidemic.
The Com-Cov trial plan is to study the efficacy of two doses of Pfizer (Pfizer), two doses of AstraZeneca (AstraZeneca) and one dose each.
All combinations work well and can stimulate the immune system.
Experts say that this discovery may bring flexibility to vaccine promotion.
The results of the trial plan also show that people who have been vaccinated with two AstraZeneca vaccines may have a stronger immune response if they receive a dose of a different brand of vaccine as a booster when they are recommended in the fall.
However, Professor Jonathan Van-Tam, Deputy Chief Medical Officer of the United Kingdom, said that there is no reason for the United Kingdom to change the plan of two consecutive doses of the same vaccine, because the vaccine is in sufficient supply and is effectively protecting lives.
But he said that this may be something that can be considered in the future: “Mixed vaccination may give us more flexibility in our strengthening plan, and it can also support those who have not reached the goal of vaccine promotion and those who may face shortages of supply. country.”
Some countries are already conducting mixed vaccination. Spain and Germany are offering Pfizer or Moderna as the second dose of messenger ribonucleic acid (mRNA) new crown vaccine to young people who have already received the first dose of AstraZeneca vaccine. This is a plan implemented after the former may cause rare but serious thrombosis and cause concern, rather than out of considerations of effectiveness.
Image source,SCIENCE PHOTO LIBRARY
Two doses of vaccines are very important to give full protection and teach the body to make antibodies and T cells to intercept and kill the new coronavirus (the picture shows the T cells attacking the new coronavirus).
Two doses of vaccines are very important to give full protection and teach the body to make antibodies and T cells to intercept and kill the new coronavirus.
The combined vaccine (Com-Cov) trial plan to vaccinate 850 people aged 50 or over with two doses of the vaccine four weeks apart, and the following findings:
- After vaccination with AstraZeneca first and then Pfizer, the antibody and T-cell response evoked are stronger than those after vaccination with Pfizer and then AstraZeneca.
- The antibodies raised by the above two combinations are higher than the two doses of AstraZeneca.
- The highest antibody response was vaccinated with two doses of Pfizer vaccine, and the highest T cell response was vaccinated with AstraZeneca first and then Pfizer.
Leading researcher Professor Matthew Snape said that these findings are not the policy reason for the UK’s decision to give people two doses of the same vaccine: “We already know that two standard vaccination plans are effective for severe and needy patients. The conditions of admission to the hospital are very effective, including two doses between 8 to 12 weeks apart to resist the Delta variant.”
He said that the new research results show that the mixed vaccination plan is also effective, although the four-week interval in the research plan is shorter than the 8 to 12-week interval that is most widely used in the UK.
“It is reported that a longer interval can bring about a better immune response,” he added.
The mixed vaccination trial plan with an interval of 12 weeks will begin next month.
Image source,Getty Images
Booster vaccination will be carried out in autumn?
At the same time, a preprint of another study was also released on Monday (June 28), which showed that adding a third dose of AstraZeneca vaccine more than 6 months after the second dose of vaccine can strengthen the immune system.
But experts say it is too early to know whether people will need to receive a third dose of vaccine before this winter. The extent to which the immune effect will diminish over time is also unclear.
Professor Paul Hunter of the University of East Anglia said: “The big question now is whether we will get a booster vaccine supply in the fall. Look at the evidence from various sources. Come, I suspect that it will probably be prepared for those who are at the highest risk of infection, either with age or clinical susceptibility.”
He suggested that based on the evidence obtained from the Com-Cov trial plan, those who have already received the first phase of AstraZeneca vaccination can receive Pfizer vaccine as a booster instead of repeating AstraZeneca vaccination. People who have passed the first phase of Pfizer vaccination may not need to receive booster doses in the fall.
analysis
BBC Medical Affairs Editor Fergus Walsh (Fergus Walsh)
The preliminary results of this hybrid vaccination experiment are very encouraging, and it also brings some interesting options for boosters.
The combination of the first and second doses of Oxford-AstraZeneca and Pfizer-BioNTech vaccines produced a strong immune response. Indeed, each method of mixed vaccination—Pfizer/Pfizer, AstraZeneca/Pfizer or Pfizer/AstraZeneca—produces stronger antibodies and cell responses than AstraZeneca/AstraZeneca.
Does this mean that two doses of AstraZeneca vaccine are worse? Not necessarily.
It is worth remembering that two doses of AstraZeneca vaccine have been confirmed to reduce the chance of hospital admission for the new coronavirus by more than 90%.
So we know from real-world evidence that the AstraZeneca vaccine is highly effective. The AstraZeneca vaccine is a “slow-burning agent”, and the immune strength is built up over time, especially when the vaccination interval is opened. The current interval between the first dose and the second dose is 8 to 12 weeks, which should make the immune response stronger.
What this trial shows is that the third booster shot may be more suitable for vaccination with a different brand of vaccine from the first two doses.
However, it is worth noting that the mixed vaccine does bring more short-term side effects, such as chills, headaches and muscle pain.