Mixing of Covid-19 vaccines: What do we know? Which countries have allowed it so far?

Countries like UK and Germany have allowed mixing of vaccines among the older generation in 'exceptional situations'

After multiple studies suggested that mixing Covid-19 vaccines was safe and effective, several countries started implementing this option due to an acute shortage of vaccines.

India's Health Ministry on Tuesday issued an advisory saying that mixing of Covid-19 vaccines was not part of the protocol yet and should not be done.

While many studies are ongoing regarding this topic, data from mix-and-match trials in Spain and the United Kingdom look promising. It suggests mixing vaccines could give higher antibody levels as compared to two doses of the same vaccine.

In the study led by Oxford University and supported by a Spanish study, people were given a dose of Pzifer’s vaccine followed by the second dose of AstraZeneca, or vice-versa. The Oxford study observed that those people showed lesser post-vaccination symptoms than those who got both doses of the same vaccine.

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In the Spanish study, around 670 people between the age group of 18-59 who had already received the first dose of AstraZeneca's Covid-19 vaccine volunteered to participate. Out of the 450 people who got a follow-up Pfizer dose, only 1.7 per cent showed side effects such as headaches, muscle pain and general malaise.

The study also found that the IgG antibodies level in the bloodstream was between 30 and 40 times higher in people who got doses of two different vaccines, than the rest.

Here's all you need to know about mixing Covid-19 vaccines:

Benefits

> Mixing vaccines will offer flexible immunisation programmes and solve supply constraints globally.

> This allows someone to receive a booster vaccine which is more effective to a new variant, in case their first dose was less effective to it.

Safety

> The UK and Spanish studies suggest that mix-and-match of two different vaccines is absolutely safe.

> The side-effects observed in both the studies were chills, fatigue, fever, headache, joint pain, general malaise, muscle ache and pain at the injection site. These side-effects resolved in some time (two to three days) and were less intense than others who got the same vaccine in both doses.

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Effectiveness

> People showed higher antibody response after 14 days of getting the booster Pzifer shot in the Spanish study. The antibodies could recognise and kill the Covid-19 virus in the lab study.

> However, there’s no evidence to say that mixing two vaccines can prevent someone from getting Covid-19.

Which countries have allowed it?

Countries like UK and Germany have allowed the mixing of vaccines in “exceptional situations” in the older generation. At the same time, the countries have warned against mixing of vaccines, unless unavoidable, while authorities continue to understand the effects of it better.

Sweden’s healthcare authorities announced on April 20 that people under the age of 65, who have had one shot of AstraZeneca, would be given a different vaccine for their second dose.

Likewise, on May 21, the Spanish government has also allowed the people below 60 years who got AstraZeneca in their first dose can get AstraZeneca or Pzifer’s booster shot.

South Korea would run a mix and match trial of Covid-19 vaccines, authorities told on May 20.

France and Norway have announced that people who got AstraZeneca’s first dose will be given an mRNA vaccine’s second dose.