Is it really safe to take one jab of Covaxin and another of Covishield?

For months altogether, the Covid-19 vaccine has been the buzzword. People have been contemplating whether to get doses of Covaxin or Covishield. While they were reportedly found to be safe and impactful during the clinical trials in their own ways, experts are contemplating mixing doses of both these vaccines to double the advantages of vaccination and offer long-term immunity to keep the virus at bay. But, the mixing should be done properly by taking all the aspects into consideration and not in a random manner.

The Covid saga continues

It has been over a year, and the country still continues to bear the brunt of Covid-19. The cases continue to escalate at a rapid rate and increased mortality and morbidity rates. The entire nation had been put under lockdown to halt the spread of the virus.  To provide that much-needed relief to people, vaccines were seen as a ray of hope, and the massive vaccination drive kicked-off on January 16, 2021.

DGCI gives a go-ahead to a study

Now, The Drugs Controller General of India (DCGI) has given a green signal for a clinical study to see whether the mixing of Covaxin and Covishield can help one safeguard against Covid-19 in India after the proposal given by the Central Drugs Standard Control Organisation (CDSCO). Hence, the permission was given to Christian Medical College (CMC), Vellore for commencing the Phase-4 clinical trial under which 300 healthy volunteers would be covered for mixing of Covid-19 vaccines Covaxin and Covishield. However, this study is different from the study conducted by The Indian Council of Medical Research (ICMR), which recently showed that mixing both vaccines can be helpful in building a better immunity against Covid-19

What does the ICMR study say?

In the study conducted by the ICMR, in May-June,  a group of  18 villagers from Uttar Pradesh were mistakenly given two different doses of Covid-19 vaccines to understand the safety and efficacy. After the first dose of Covishield, the second dose of Covaxin was given after 6 weeks. Then, this ICMR study was compared with other 40 recipients who got 2 doses of Covishield and 40 vaccine beneficiaries who got 2 doses of Covaxin.

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According to the ICMR, the study revealed that mixing doses of Covaxin and Covishield gives results in building a strong immunity to fight Covid-19. The findings of the study suggest that the heterologous vaccination triggers a good antibody response when compared to the 2 shots of the same vaccine that is Covishield or Covaxin.  The study is published as a pre-print but yet to be peer-reviewed.

The mix and match approach

1. Mixing and matching of the vaccine is a long-debated topic. But, finally it has received a go-ahead now for tackling low efficacy rates and generating a better immune response by administering one dose of Covishield and the other of Covaxin.

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2. Mixing and matching the doses will remove hesitation in the minds of people when it comes to inoculation, and one can complete his/her vaccination shots.

3. Currently, there are not many studies available about the mix and match approach. A detailed analysis is required to study the combination of these vaccines.

Is the mixing and matching of Covishield and Covaxin beneficial?

• Covishield is known to generate an anti-spike protein response along with an anti-adenovirus response. Covaxin, used as a booster, may boost anti-spike response further and generate a primary response against all other SARS-CoV-2 proteins that form the part of the preparation of  Covaxin.
• The study conducted by the ICMR has shown how the heterologous vaccination tends to generate an anti-N-protein response owing to a boost with Covaxin. Anyway, further data is still needed to know about the mixing of any of the vaccines. It is essential to understand the vaccines thoroughly, and which vaccines induce what type of immune response, what needs to be the correct sequence and the durability of the immune response, and only then the people should be vaccinated via a mix and match approach.

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Has the mix and match approach been tried anywhere else?

This type of approach was adopted by Europe when the AstraZeneca vaccine was revealed to be linked with blood clotting in some people. A second dose with a different vaccine, especially mRNA was recommended by many countries when it came to the younger population. Still, there is no detailed information regarding this.