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- India on Tuesday reported 8,813 Covid cases and 29 fatalities. The cumulative caseload is 4,42,77,194 (1,11,252 active cases) and 5,27,098 fatalities
- Worldwide: Over 591 million cases and over 6.43 million fatalities.
- Vaccination in India: Over 2.08 billion doses. Worldwide: Over 12 billion doses.
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| TODAY’S TAKE |
| How well does hybrid immunity protect against SARS-CoV-2? |
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- About 75% of people across the globe are likely to have immunity against Covid-19. However, hybrid immunity, which is a combined immunity conferred by both vaccination and natural infection, is found to be the most effective of all preventatives.
- The study: Individuals with hybrid immunity have about 50-fold higher neutralising antibody (nAb) titers as compared to recovered unvaccinated individuals. A new study published in Nature Reviews Immunology journal explores the reason behind this enhanced protection.
- The findings: “Vaccination after infection with the ancestral strain or with subsequent variants increases the number of SARS-CoV-2 memory T-cells and B-cells by more than an order of magnitude by recruiting new B-cell clones into the memory pool,” reads the study. The clonal expansion of persistent immune cells also contributes to hybrid immunity.
- T-cells are white blood cells that can remember past diseases, attack virus-infected cells or help in production of antibodies to counter them. The other memory cells, B-cells, are generated by vaccines and play a role in determining the specificity of immune response to foreign pathogens in the body.
- The team found that breakthrough infection with the Omicron variant leads to an enhanced breadth of neutralising activity against other variants as well, including the ancestral and Delta variants. But in unvaccinated individuals subsequently infected with the Omicron variant, this cross-neutralising activity is absent.
- Though the unjabbed group exhibits nAbs against Omicron BA.1, the titers are six-fold lower after breakthrough BA.1 infection as compared to the corresponding anti-Delta nAb titers after a breakthrough Delta infection.
- Implications: It may be time to change the current ‘one shoe fits all’ approach. “In a highly dynamic immune landscape with its various degrees of natural, artificial and hybrid immunity and the regional circulation of Omicron sublineages, vaccination strategies need to be tailored on a regional, perhaps even personalised, basis,” reads the study.
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| TELL ME ONE THING |
| Another study proves that face masks reduce Covid transmission |
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- Pandemic fatigue, masking troubles, false bravado about being immune to Covid-19, talk about herd immunity or a combination of the above are driving many to forego face masks in public, unless there’s a specific government diktat.
- For instance, in the US, following the updated guidelines from the Centers for Disease Control and Prevention (CDC) in February 2022, many state-wide restrictions mandating masks in schools and community settings were lifted.
- But while the Massachusetts Department of Elementary and Secondary Education removed mask requirements in schools, only two school districts – Boston and Chelsea – out of 79 sustained masking requirements until June 2022.
- This gave researchers from Boston Public Health Commision and Harvard University a unique opportunity to assess the real impact of masking in schools.
- The team used district-level data from DESE on Covid-19 cases, enrollment, and staffing for the 2021-22 school year.
- Over 2.94 lakh students and 46,530 staff were included in the study. Additional data on infection indicators from the surrounding communities were obtained from the Department of Public Health.
- The study found that lifting mask mandates was associated with substantial increases in the case rates in 12 of the 15 weeks.
- “We estimate that lifting of school masking requirements was associated with an additional 44.9 Covid-19 cases per 1,000 students and staff over the 15 weeks since the lifting of the statewide school masking requirement, representing nearly 30% of all cases observed in schools during that time,” read the study recently posted to the medRxiv* preprint server.
- This translates to a minimum of over 17,000 days of school absence for students or over 6500 days of teacher absence in the best-case scenario.
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Written by: Rakesh Rai, Sushmita Choudhury, Jayanta Kalita, Prabhash K Dutta
Research: Rajesh Sharma
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