How long will the vaccine-induced immunity against COVID-19 last? This is a question that is on the minds of many. A study conducted by a team of researchers at AIG Hospitals here in collaboration with Asian Healthcare Foundation has shown that around 30% of the fully-vaccinated population likely to lose immunity in as less as six months.
The cross-sectional study conducted on 1,636 healthcare workers and support staff, who had taken both doses of the vaccine. A majority of them were above the age of 40 years with co-morbidities such as hypertension and/or diabetes. The preprint of the study was published in Research Square on January 14 this year.
Pointing to the results, the researchers said individuals above 40 years with diabetes and hypertension of both genders may be at a higher risk of SARS-CoV-2 infection and these individuals should be prioritised for a booster dose after six months of their second jab.
The healthcare workers chosen for the study were drawn from various departments and included clinicians, residents, nurses, laboratory personnel, research scientists, security staff and transport personnel.
“The aim of the study was to understand the effectiveness of current vaccines over long term and see if there is a specific population demography which needs a booster at the earliest,” said AIG Hospitals chairman D. Nageshwar Reddy.
Along with him, the other doctors who were part of the study included Sasikala M. and Apoorva Munigela.
The researchers measured the IgG anti-S1 and IgG anti-S2 antibodies to SARS-CoV-2 in the participants.
Of the 1,636 participants, 93% received Covishield, 6.2% opted for Covaxin, and less than 1% had taken Sputnik V.
Dr Nageshwar Reddy said antibody levels were checked four weeks, six months and nine months after the participants got the second dose.
“Our study results were at par with other global studies where we found that almost 30% individuals had antibody levels below protective immunity level of 100 AU per ml after six months. These individuals were majorly above 40 years with co-morbidities like hypertension and diabetes. Of the total, 6% did not develop any immune protection at all,” he added.
The senior doctor stressed that the population above the age of 40 years, especially those with co-morbidities, are more prone to develop the infection after six months of being fully vaccinated and therefore, should also be considered for the precautionary dose.