Mixing Covishield and Covaxin yields better results: ICMR Study

Combining Covishield and Covaxin elicited better immunogenicity than two doses of the same vaccine, reveals a study by ICMR. It found that immunization with combination of Covishield and Covaxin was safe, and the adverse effects were also found to be similar when compared to the same dose regime.

This study – “Serendipitous COVID-19 Vaccine Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime” involved 98 people, 18 of whom had inadvertently received Covishield as first dose and Covaxin as the second. Researchers highlighted that this is the first study which reports the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine.

The immunization programme against COVID-19 in India, as per PTI, started with two vaccines – adenovirus vector platform-based vaccine Covishield and inactivated whole virion BBV152 – Covaxin and homologous prime-boost approach was followed. However, 18 individuals under the national program, in Siddarthnagar, Uttar Pradesh inadvertently received Covishield as the first jab and Covaxin as the second.

The nationwide vaccination program at this time had entered in its fourth month of its existence and the event of mixed dosing raised considerable anxiety in public domain with a potential to contributing to vaccine hesitancy. The study was conducted against this backdrop. So, including these 18 individuals who had received one dose of Covishield and second dose of Covaxin, 40 recipients of two doses of Covaxin, were recruited in the study. The study duration was from May to June 2021.

It compared the safety and immunogenicity profile of the 18 individuals against that of those receiving either Covishield or Covaxin. Lower and similar adverse events following immunization in all three groups underlined the safety of the combination vaccine-regime. Immunogenicity profile against alpha, beta and delta variants in the heterologous group was superior and IgG antibody and neutralizing antibody response of the participants was also significantly higher compared to that in the homologous groups.

The findings suggest that immunization with a combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was not only safe, but also elicited better immunogenicity. The reactogenicity analysis was carried out based on solicited local and systemic AEFIs reported in the three groups within seven days of immunization. None of the participants enrolled in the study had any seriou0073 AEFI within 30 minutes of immunization with the first or second dose. The most common local AEFI reported after first and second dose was pain at injection site.

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No other local AEFI such as erythema, induration, pruritis or pustule formation was recorded by any of the participants. Most commonly reported systemic AEFI were pyrexia and malaise. No other systemic AEFIs like urticarial, nausea, vomiting, arthralgia or cough was reported. The pyrexia was of low to moderate grade and was managed by administration of paracetamol and subsided in all participants within three to four days post vaccination.