Although the World Health Organization believes that vaccines are the only possibility to achieve herd immunity, two major clinical trials have been temporarily halted due to unexplained diseases. Mint looks at how long it would take for the immunization campaign to materialize.
How do we describe herd immunity?
When the majority of the community is immune to an infectious disease, either through vaccination or previous disease, the spread of the disease from one person to another is reduced, leading to herd immunity. It is calculated from the reproductive number or the number of secondary infections caused by an infected person. However, this varies for each type of infection. For covid, experts estimate that 70% of the population must be affected for the community to achieve herd immunity. With a population of around 1.3 billion people, India will have to vaccinate about 900 million people to achieve herd immunity.
How has vaccine development progressed?
Globally, 42 vaccines are undergoing human trials at the moment, with another 151 in the preclinical stage. In India, three vaccines – from the Serum Institute of India, Bharat Biotech International and Zydus Cadila – are in human trials and a half dozen more are in the preclinical stage. The Serum Institute candidate is in phase 3 of the trial, while the other two are in phase 2. At least one candidate is expected to be approved by the end of December or early next year, and commercialization can begin in June 2021. While vaccines take at least five years to develop, covid candidates go through all three testing phases in one year.
See full image
Have any of the vaccine trials faced safety concerns?
The AstraZeneca trial was halted last month, while the Johnson & Johnson study was also temporarily halted due to an unexplained illness in one participant each. In the J&J trial, the hiatus is not a major concern, with no clarity on what caused the illness. For AstraZeneca, all global regulators, except the US FDA, allowed the resumption of trials after a comprehensive review of safety data.
How will the logistics work after the vaccine?
India has the largest vaccine manufacturing capacity and the Serum Institute is the world’s largest producer by volume, with an annual capacity of more than 1 billion doses. Bharat Biotech and Zydus Cadila plan to produce at least 200 million and 100 million doses per year. However, the Bharat Biotech and Serum vaccines require two doses, while the Zydus Cadila vaccines require three doses. While India can produce 1 billion syringes a year, about half will go for export. Cold storage and transportation are central to India’s immunization plan.
Who will receive covid vaccines first?
WHO and governments around the world are developing guidelines that prioritize people who are at high risk, including front-line workers like healthcare executives and the police, in addition to the elderly and people with comorbidities. On Wednesday, the WHO said young and healthy may have to wait until 2022 to receive the covid-19 vaccine. The whole immunization process could take up to three years. However, since clinical trials are short, we will not know how long the vaccines will provide immunity.
.
