Is it safe to mix Covid-19 vaccines?
Amid discussions around booster vaccines, combining different Covid-19 vaccines is being seen as a technique to boost immune efficacy.
It's been almost a year sinceCovid-19 vaccinevaccinations began around the world. A lot has changed since then. From new variants emerging to waves of Covid-19 in many countries. There are also recent concerns about waning immunity and cases in vaccinated people.
Reasons why mixed injections are becoming more popular
Scientists say the new variants are more contagious and more worrisome than the original strain, and they fear that current vaccines may not be as effective against the SARS-CoV-2 virus. In addition, vaccine-induced immunity is waning, leading to an urgent need for booster shots.
Amid discussions around booster vaccines, combining different Covid-19 vaccines is being seen as a technique to boost immune efficacy.
In fact, many countries have previously allowed the mixing of two different vaccines. For example, the first dose is the AstraZeneca vaccine, the second dose is the Moderna or Pfizer vaccine.
Even top world leaders are opting for this option. German Chancellor Angela Merkel, 66, received a second dose of the Moderna vaccine after receiving her first dose of AstraZeneca. In Italy, Prime Minister Mario Draghi, 73, received AstraZeneca and Pfizer. Canadian Prime Minister Justin Trudeau received AstraZeneca and Moderna.
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| Illustration: QZ |
A Lancet study found that mixing doses of the AstraZeneca vaccine with mRNA vaccines (Moderna, Pfizer) produced a stronger immune response against the SARS-CoV-2 virus than two doses of AstraZeneca. The evidence now shows that the injection technique is safe.
Additionally, with a large number of people still waiting to be vaccinated for themselves and their loved ones, combining Covid-19 vaccines would increase flexibility.
Is mixed injection safe?
Mixing different doses of vaccines may sound unusual, but to immunologists, it's nothing new.
The Ebola vaccine developed by Johnson & Johnson is an example of an effective combination vaccine that provides long-lasting immunity. The first shot uses an adenovirus similar to the AstraZeneca vaccine. The second shot uses a modified version of a poxvirus.
However, British scientists noted that people who received the AstraZeneca vaccine and then the Pfizer vaccine had more side effects such as fever, chills, headache, muscle fatigue and joint pain than those who received two doses of the same vaccine.
However, no one needs to be hospitalized because these symptoms are short-lived.
