by Dr. Nell Thomas
I’m looking around the world and see vaccination rates vary from country to country. More than 448 million vaccine doses have been administered worldwide, equal to 5.8 doses for every 100 people, globally.
But there is a large discrepancy among countries. Israel continues to be vaccinating faster than any other country, with 109 vaccines delivered per 100 citizens as of March 22 (58 per cent have received one shot and 50 per cent have had both shots and are fully vaccinated). Canada has given 11.74 shots per 100 people (9.9 per cent have received first dose, and 1.9 per cent have received second dose). While some countries have not yet given even a single dose.
Most countries seem to be prioritizing fully vaccinating people. For example, the US has given 38 shots per 100 people, with 25 per cent having one shot and 13 per cent having had two shots. Britain has had a different approach, focused on broadly vaccinating the population with one shot. They have completed 41 doses per 100 people, with 38 per cent having had one shot and only 2.6 per cent of the population fully vaccinated. By maximizing the number of people with one vaccine, and delaying the second shot by three months, they have broader mass protection.
What our science tells us so far is the second vaccine will increase your immunity by only about 10 per cent in the first few months. The purpose of the second shot is to provide longer immunity. How long, we don’t know. But we do know that a single shot provides strong protection now, and for at least a few months. Experts are in agreement that delaying the second shot will diminish the ultimate effectiveness by only a negligible amount.
Is Britain’s approach working? Since early January, the daily number of new cases in Britain has fallen by more than 90 per cent. This is a larger drop than in almost all countries. Especially impressive given that the B.1.1.7 variant is their dominant strain and is more contagious than the original strain. Deaths continue to plummet in Britain. And they are using the Astra Zeneca vaccine, with no increase in diagnosed blood clots, and despite its slightly less effectiveness than Moderna and Pfizer, the British population is clearly reaping the benefit.
In contrast, worldwide, the number of confirmed COVID cases has increased 21 per cent in the past month.
People who study disease transmission use a term called the “R nought” (R0) to describe how contagious a disease is. It refers to the reproduction number of a disease. The number placed behind the R indicates how many people are likely to be infected by one individual with the disease.
For measles, the R0 is 12-18, meaning it is very contagious, as one individual can infect 18 others. If the R0 is greater than one, then each person is infecting more than one other individual and the disease will continue to increase in the population.
In Britain now, the R0 for COVID-19 is less than one, meaning the infection is no longer spreading. (Annual influenza has an R0 of 0.9-2.1).
In Ontario, as of March 18, the reproduction number (R0) for the new COVID variants of concern (the more contagious strains with the N501Y mutation) is 1.25, and the R0 for other variants without this concerning mutation is 1.07. Anything above one indicates exponential increase in growth, and the higher the number, the faster the infection will transmit. We are in a race to get as many people vaccinated as possible before these more contagious variants are widely circulating.
Stay tuned to all the fact-based resources for how to get swabbed (tested) and how to get vaccinated.
