BHUBANESWAR: The decision by global pharmaceutical major AstraZeneca to withdraw its Covid-19 vaccine Covishield has reignited the debate and discussion around vaccine efficacy and adverse events following immunisation (AEFI).
Produced by Serum Institute of India (SII), Covishield was jointly developed by AstraZeneca and Oxford University. The Cambridge- headquartered bio-pharmaceutical company had introduced the vaccine as Vaxzevria in the UK and European Union.
So far, around 175 crore doses of Covishield have been sold and it is the most widely administered vaccine in India. In a UK court, AstraZeneca recently admitted that its vaccine could lead to thrombosis with thrombocytopenia syndrome (TTS), a condition that results in blood clotting and low platelet count.
Despite widespread vaccination, a very limited number of TTS cases have been documented in the country. However, the revelations regarding the potential rare side effect and subsequent withdrawal of the vaccine have sparked concerns. SII has made it clear that the withdrawal has nothing to do with the legal battle and attributed it to the decline in demand.
Rare side effects
Rare side effects refer to adverse reactions that occur infrequently among the vaccinated. It could be one in one lakh vaccinated population or it could be one in one lakh doses administered. These side effects are typically observed in a small percentage of vaccine recipients. Examples of rare side effects associated with Covid vaccines include pericarditis, myocarditis and blood clotting.
AstraZeneca and SII had earlier disclosed the rare side effects of the vaccine in product inserts. Noted epidemiologist Dr Jayaprakash Muliyil said there is an old teaching that if a drug has no side effects, it has no effect at all. This goes without saying that vaccines may have side effects that are very rare. “But there is still confusion over adverse events after vaccination, as it is difficult to know whether they are vaccine-induced or due to Covid infection. In fact, vaccines are beautiful ways of preventing diseases,” he said.
On withdrawal of Covishield, the former principal of Christian Medical College, Vellore, said the usefulness of the particular type of vaccine is over. “After the Omicron variant arrived, everybody got infected. Omicron is an immune escape variant and it produced many sub-variants. This series of variants made sure people were immunised whether vaccinated or not. Omicron gave people very good lasting immunity against all previous variants like Alpha and Delta.
People who were infected by Omicron or its sub-lineages got natural immunity. Covishield was manufactured for the first series of variants. It has no value now,” he said.
Risks & side effects
The duration of the risk of rare side effects associated with Covid vaccines can vary depending on several factors, as different vaccines have varying risks. The risk of rare side effects may differ among various demographic groups, such as age, sex, and underlying health conditions. Eminent virologist and public health expert Dr T Jacob John said TTS is one of the rare side effects and generally such cases are mostly reported within a few weeks of vaccination.
“The side effects do not occur after two or three years of vaccination. People should not worry and panic as not everyone who receives the vaccine will be affected by TTS,” he clarified. Dr E Venkata Rao, principal investigator of the human trial of a Covid vaccine, however, differs. He said theoretically, all those who were administered with the vaccine are at risk of side effects, but not randomly. For example, he said, an alcoholic person may be at a higher risk compared to a person who is physically fit due to a regular yoga practice.
“Yes, side effects can occur after two to three years. But that is very rare,” said Dr Rao, professor of community medicine at IMS and SUM Hospital, Bhubaneswar.
Call for review of vaccines
A group of doctors under the banner of Awaken India Movement has urged the union government to review the science behind all Covid vaccines and stop the fear mongering against vaccines. They have demanded an audit of their commercialisation as well as implementation of active surveillance and monitoring mechanisms to ensure vaccine adverse events are identified at the earliest. The body said the product insert of Covid vaccines was never seen by people taking the shot and the government never considered prior informed consent a necessity.