The Covid-19 outbreak in India is pretty scary now, with a really steep increase in new cases and deaths in just a few weeks.
https://www.theguardian.com/world/2021/apr/19/what-do-we-know-about-the-indian-coronavirus-variant
There was an interesting article March 1, 2021 about why poorer regions like India and Africa did not have huge outbreaks of Covid-19. While many possible reasons were given, the overall conclusion was that it is somewhat of a mystery. It was written by Siddhartha Mukherjee, a brilliant doctor and writer who won a Pulitzer Prize for the book “The Emperor of All Maladies. A Biography of Cancer”. This is a long article but worth reading, or listening to. It is not often that you will read such a well written piece on the pandemic.
https://www.newyorker.com/magazine/2021/03/01/why-does-the-pandemic-seem-to-be-hitting-some-countries-harder-than-others
Now there is a partial answer to the mystery. It took time for a mutation to adapt to the particular conditions of India. Now that it has, the virus is taking off.
The spike in cases in India is actually a similar trajectory (slope) as the UK variant was in Britain. But because the population of India is 20 times that of the UK, there is a huge difference in the number of people who are getting sick and dying. The UK variant peaked at over 50,000 cases. With a factor of 20, it is possible that daily new cases in India could rise to 1,000,000.
The UK was able to recover with a hard lockdown at the beginning of January and an aggressive vaccination program. Once the UK vaccination rate reached 50%, spread of the virus started to slow down.
It won’t be easy for India to do this. They need to vaccinate over 500 million people to reach 50%.
https://ourworldindata.org/grapher/covid-vaccination-doses-per-capita?country=CAN~GBR~USA~IND
Typical estimates for herd immunity reported in the media are when 60-80% of the population has immunity. In fact my model shows much lower thresholds. Herd immunity depends on a combination of factors:
number of prior infections1 + number vaccinated + transmission rate
1A recent study has confirmed that people who recover from Covid-19 do in fact acquire immunity.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00675-9/fulltext
My U.S. model shows herd immunity at 50%, with cases starting to decline in mid April (as reflected in the graphs above).
If Canada can keep the transmission rate low at 1.1 we will see slowing cases when vaccination reaches 40% of the population, which will be mid May.
This model assumes that vaccines continue to work against the variants active in Canada. There’s plenty of evidence, from both vaccine clinical trials and real world data that all the vaccines protect against these variants, but there is not enough information yet about the India variant.
https://www.healthline.com/health-news/covid-19-vaccines-are-still-effective-amid-rising-number-of-variants
Another assumption is that Canada will receive vaccines according to the contracted agreements with suppliers.
https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection/prevention-risks/covid-19-vaccine-treatment/vaccine-rollout.html#a4a
