Neutralising antibody responses against the SARS-COV-2 virus and its variants of concꦗern (VoC) are highe𓆉r among Covishield recipients than those who took the indigenously made Covaxin, according to a multi-centre study.
The yet-to-be peer-🐼reviewed study, posted on the preprint server MedRxiv on Friday, also found that when compared to pre-vaccination baseline, both vaccines elicited statistically significant antibody levels in both seronegative individuals and seropositive or those who had recovered from Covid-19 infection.
Between June 2021 and January 2022, the researchers enrolled 691 parti൩cipants in the 18-45 age group across four sites♎ in urban and rural Bengaluru and Pune.
Participants received either two dos🔜es of Covaxi🍬n at 28 days apart or two doses of Covishield at three months apart.
The Omicron wave in early 2022 overlapped with the second dose of vaccine in two sites and with both doses in one🍰 site.
Participants were sampled at six timepoints for antibody analyses an🐭d at four timepoints for cellular analyses.
When compared to pre-vaccination baseline, both vaccines elicit๊ed statistically significant antibody levels in both seronegative and seropositive individuals, the researchers found.
Covishie🅰ld elicited immune response🍃s of higher magnitude and breadth than Covaxin in both seronegative individuals and seropositive individuals, across cohorts representing the pre-vaccination immune history of the majority of the vaccinated Indian population.
Immunologist Vineeta Bal noted that in young adult population there is a difference in the response to Covid vaccines, if individuals are already infected with SARS-CoV-2 and recovered (s🐼eropositives) versu𒈔s not infected.
"In seronegatives, two doses of Covishield lead to higher magnitude of antibody levels in higher proportion of vaccine recipients as compared to Covax🌞in recipients," Bal, from Indian Institute of Science Education and Research (IISER), Pune and one of the study authors, told PTI🐈.
"In terms of waning of immune response with time also Covishield vaccinated individuals retain antibodies in their blood for longer period in large𒀰r proportion of individuals,” she said.
The study does not directlyඣ look for or document protection from COVID-19 in the recipients.
"Levels of n♍eutralising antibodies as wel𒅌l as T cell responses, according to different investigators, are indirect indicators of protection,” Bal said.
"The interim results so far show that Covishield♏ vaccination induces robust neutralising antibodies against the original SARS-CoV2; Covaxin also does it but somew🥃hat less efficiently,” she added.
"Against later variants of the virus such as Delta and Omicron, especially Omicron, neutralising antibodies triggered⭕ by Covishield are not as effective, however, they appear marginally better than in Covaxin recipients," Bal added.
Prior studies🍰 comparing Covishield and Covaxin were limited to addressing only antibody responses and in particular in the health care worker population who were immunised prior to the Delta wave.
There is, however, limited data on cellular immune response💦s elicited by thes♓e vaccines and no direct head to-head comparisons or stratification by pre-vaccination serostatus.
Vaccination following exposure to the Delta or Omicron variants of SAꦍRS-CoV-2 is likely to affect the quality, quantity and duration of immune responses.
For determining future♒ COVID-19 vaccination policy when pan-coronav🔜irus or sarbecovirus vaccines become available, it becomes important to take into account pre-vaccination immune history of the majority of the vaccinated Indian population.
"Some unpublished work from other investigators in India seems to suggest that 𓆉heterologous boosting i.e. Covaxin in Covishield recipients and vice versa works 🅠better than homologous boosting," Bal added.
