A study that included 98 individuals, of which 18 had been accidently administered a fist dose of Covishield and Covaxin as the second dose in Uttar Pradesh, revealed that combining the two vaccines evoked better immunogenicity compared to two doses of the same vaccine.

The study, conducted by ICMR, noted that vaccination with a combination of Covishield and Covaxin was safe and the adverse effects appeared to be similar to the same dose regimen. The study is titled ‘Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime and has been posted on the preprint server medRxiv, and awaits peer review.

Researchers stated that as per their knowledge, this is the first study to report the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine.

A total of 18 people in Siddarthnagar, Uttar Pradesh accidentaly received Covishield as the first vaccine dose and Covaxin as the second dose under the national COVID-19 vaccination program. This mixed dosing event raised concerns among people with a potential to lead to vaccine hesitancy. Hence, the study was conducted.

Apart from the 18 individuals who had been administered one dose of Covishield and second dose of Covaxin, 40 individuals who had received two doses of Covishield and 40 who had been given two doses of Covaxin, were included in the study. The duration of the study was from May to June this year. The safety and immunogenicity profile of these 18 individuals was compared with that of those who had been administered either Covishield or Covaxin. 

The immunogenicity profile against the variants Alpha, Beta and Delta appeared to be superior and IgG antibody and neutralizing antibody response was significantly higher in the heterologous group, compared to the homologous groups. 

The study thus suggested that inoculation with a combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was safe and evoked better immunogenicity.

The reactogenicity analysis was based on the local and systemic AEFIs reported in the study groups within seven days of vaccination. There were no serious AEFIs in any of the study participant within 30 minutes of immunization with the first or second dose. The most common local AEFI following first and second dose was pain at injection site.

No other local AEFI was reported by any of the participants. Pyrexia and malaise were the most commonly reported systemic AEFIs. No other systemic AEFIs were reported. The pyrexia was of low to moderate grade and was managed with paracetamol. It was relieved in all participants within three to four days after immunization.

Though the median age of the participants of the heterologous group was high (62 years), the reactogenicity profile suggested that mixing of the two vaccines was safe.

The mixed regimens for vaccination can help to overcome the challenges of shortage of particular vaccines and eliminate vaccine hesitancy. The study highlighted that to conclusively confirm these findings, a multicenter randomized controlled trial is needed.

Source: ET Healthworld