Introduction 

Currently in India, the world’s largest vaccination drive is being carried out. For now, anyone above the age of 18 can be vaccinated under the programme, provided they don’t have an active COVID-19 virus or aren’t allergic to the vaccine. Even lactating mothers are eligible to get inoculated after consultation from a gynaecologist. 

Missed second dose: What happens next? 

According to current virology research, any person needs to get two vaccine dosages for a complete immunity response against the COVID-19 virus. Hence, skipping a dose is not an advisable option.  

However, what happens if a person doesn’t get the second vaccine dosage in the said time frame due to any reason?
The non-availability of the second dose will not affect the immunity received from the first dose. Although it is critical to get the second jab as soon as possible, do not skip taking it if you have surpassed the recommended timeline.

Covishield and Covaxin: Can the two be mixed?

In an interesting case in India, 20 people from Uttar Pradesh’s Siddharthnagar were given two different vaccines as their first and second dose. Their first dose was Covishield, whereas six weeks later, they were given a shot of Covaxin as their second dose.

So far, the people who were given a cocktail of these vaccines have not reported any side effects. However, the incident has begun an inquiry to study the effectiveness of administering two different vaccines on immunity.

The centre is carrying out a multitude of studies to understand whether mixing COVID-19 vaccines is possible. They have highlighted three major reasons to carry out the mixing of COVID-19 vaccines:

• Convenience:
  Vaccination shortage is one of the biggest challenges stopping people in India from getting vaccinated. In several regions, at a given time, either Covaxin or Covishield may be available. By mixing the two vaccines, many masses may have a shot at getting vaccinated, especially in rural areas where there is a fluctuation in the supply of the vaccines.

• No threat to safety:
  So far, the studies being carried out in this area have not reported any side effects or threat to the person taking two doses of different vaccines. If there is no threat to safety found after mixing the two vaccines in the long run, the centre may consider it.

• Better immunity response

The ongoing debate on Covishield v/s Covaxin will soon be put to rest if a better immunity response is achieved after mixing them. Although they have entirely different mechanisms, the centre is sure that combining them will yield positive results. 

Mixing of vaccines is good as research found people produced antibody responses from all three booster vaccines, no matter which vaccine they had originally received. A booster of a different vaccine caused similar or higher antibody responses than a booster of the same vaccine

Dr. M.G. Kartheeka, MBBS, MD

What other countries are testing the feasibility of mixing two different vaccines across the world?

India is not the first country to consider ‘mixing ‘ the vaccines for further use. Several countries like the UK, USA and Spain are also testing various combinations of the vaccine.

Oxford University is conducting trials between its Oxford-Astrazeneca vaccine and Pfizer vaccine. While some people administered a cocktail of these vaccines reported mild side effects, the majority said none.

The UK, Germany and France have already given the green light for combining the two vaccines in exceptional cases, especially for older populations. More trials to understand the efficacy of the combined vaccines is still underway.

Even a study conducted in Spain, where they vaccinated people with both OxfordAstraZeneca and Pfizer’s BioNTech, reported developing a potent immune response against the COVID-19 virus.

A similar experiment is being conducted in the USA between Moderna’s and Pfizer’s COVID-19 vaccines.

Some experts have reported that combining the vaccines may be necessary if the virus mutates in the long run. Even a booster dose of a different vaccine may be essential if limited immunity has been achieved from two doses of the same vaccine.

Although studies revealed that there were higher immunogenic reactions to the booster of a vaccine than the primary vaccine, these being milder and resolved with paracetamol, this different booster elicited a better immune response and this response improves over time.

Dr. Ashish Bajaj, M.B.B.S., M.D.

Can India achieve its vaccination targets by mixing the vaccines?

The Indian Government has successfully distributed over 23 crore vaccines to all states in India. The centre is planning to procure over 75% of the vaccines directly from the manufacturers and is gearing up to provide free vaccines to everyone over 18.

Dr NK Arora (Chairman of National Technical Advisory Group on Immunisation) said that, if found effective, the mixing of both Covishield and Covaxin can boost India’s vaccine drive by several folds.

The feasibility of mixing COVID-19 vaccines could easily amplify India’s administration to 20 – 25 crores per month. It is almost a 50% boost in supply and may help achieve India’s Vaccination target.

Conclusion

The vaccines Covaxin and Covishield have been approved for people over the age of 18. However, given the large number of people residing in India, most of them concentrated in the rural regions, immunising the entire population is a mammoth task. 

While many people think that the mixing of COVID-19 vaccines may help to make up for the vaccination shortage in India, but it is important to understand that it will require thorough testing and research to ensure its safety and effectiveness. As per the current studies and advisories, it is not allowed to mix two doses of different vaccines. You have to take the second dose of the same vaccine you took your first jab with.

The Head of India’s COVID-19 Taskforce, VK Paul, in an interview, has said that it is ”scientifically and theoretically” possible to mix the two vaccines. However, it will require “robust scientific evidence” to be carried out.

Without appropriate evidence, mixing two vaccines may prove to be more lethal than useful and endanger the lives of thousands of people. But, if it is found to be successful and safe, the centre will implement it in the near future.

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