Updated: January 13, 2022 7:37:38 am
In an indication of weakening of antibody response among the fully vaccinated over time and thereby a need for booster dose, fully vaccinated individuals in Mumbai showed a spike in fresh infections of over 150 per cent in the last couple of months.
Data sourced from the Brihanmumbai Municipal Corporation (BMC) shows that while breakthrough infections among fully vaccinated beneficiaries stood at 15,565 between February 1 and November 7, the numbers jumped to 40,536 as on January 4, 2022 – 154 per cent rise in two months.
By comparison, breakthrough infections among the partially vaccinated individuals rose from 16,933 till November 7 to 18,356 on January 4, 2022, witnessing a rise of 8.4 per cent.
Thus, the infection rate among fully vaccinated was high at 0.5 per cent as against 0.18 per cent for partially vaccinated individuals for the 11-month period between February 1, 2021 and January 4, 2022.
While 1.81 crore individuals were inoculated with at least one dose of vaccine against Covid-19 in Mumbai between February 1, 2021 and January 4, 2022, data shows that 99,95,739 individuals have been administered the first dose and 81,37,850 beneficiaries have received both the doses.
While 18,356 or 0.18 per cent of the partially vaccinated got infected with Covid-19, 40,536 fully vaccinated beneficiaries got infected – 0.50 per cent breakthrough infections among fully vaccinated people.
This however, is in sharp contrast to the infection trajectory recorded two months ago in November 2021, when the pandemic curve had flattened. Data shows that between February 1 and November 7, 2021, of the 35,24,653 individuals who took the first dose, 16,933 contracted Covid-19, counting as 0.48 per cent breakthrough infection.
By comparison, the infection rate among fully vaccinated beneficiaries was 0.30 per cent, as 15,965 individuals of the 53,83,945 who had taken both the doses were infected.
Doctors attribute the spike in fresh infections among fully vaccinated individuals to factors such as withering of immunity over a period of time and a more casual Covid-19 appropriate behaviour.
“It could mean that individuals, who received the first dose recently (November 2021-January 2022), had higher antibody responses and thus, reported lesser breakthrough infections as compared to fully vaccinated individuals who received both doses prior to November 2021,” said Dr Harshad Limaye, senior infectious disease expert, Nanavati Hospital.
BMC Additional Commissioner Suresh Kakani also said that this could be because of the fact that the antibodies from the vaccines start weakening after nine months of immunisation. “As a majority of the existing fully beneficiaries were vaccinated 8-10 months ago, their immunity might have become weak, making them vulnerable to contracting the infection. Thus, the demand for booster shots was raised,” he added.
While the mass immunisation programme started from January 16, 2021, the gap between the first and second dose was initially set at 4-6 weeks for Covishield vaccines. It was later increased to 6-8 weeks in April and then further increased to 12-16 weeks. So, many who received their first dose in January and February 2021, received their second dose over the next two months.
Doctors also highlighted that many fully vaccinated individuals put their guards down and avoided core preventive measures such as masking, washing hands or social distancing after taking both the doses and that could have also led to the spike in breakthrough infections among them.
“One major reason for this interesting statistical trend could be restricted access for partially vaccinated individuals to malls, cinema theatres, restaurants, flights and other public places and transport channels. Easy access to public places for fully vaccinated naturally increases the chances of infection,” said Dr Limaye.
However, Dr Rahul Pandit, a member of the state Covid-19 task force, said that the rise in breakthrough infection rate doesn’t hold much importance, as the severity among such patients is minimal. “It is more important to focus if the infection in these 0.50 per cent patients progressed to severity and required ICU or oxygen support or lead to mortality. Vaccines may or may not prevent breakthrough infections, but they can certainly provide very good immunity against severe disease,” he added.
On Wednesday, The Indian Express had reported that 94 per cent of the total 4,575 Covid-19 deaths in Mumbai between February 1, 2021 and January 4, 2022, were of unvaccinated patients. The remaining 6 per cent or 255 patients who lost their lives to Covid-19 were vaccinated.
Following this, Mumbai Mayor Kishori Pednekar, in a recorded video message, advised people to get fully vaccinated to avoid the severity of infection.
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