Effective Reproduction Number

Coronavirus COVID-19 living through pandemic

The virus outbreak could be stopped or slowed down when effective vaccine exists. Vaccine, as you remember, is only preventive and hence must be applied to a healthy person before the first infection to increase immunity. The same effect would be achieved if someone had already the disease earlier and survived – the immune cells will retain the memory of the pathogen.

When part of the population is immune to the virus as a result of surviving the virus or vaccination, R number will be affected. So, if 30% of population becomes immune, R will be multiplied by percentage of susceptible population (100%-30% = 70%). R then becomes lower and disease decline is possible. 

This new R is called the Effective Reproduction Number and denominated as Re or simply R.

R = R0 * x, where x is the fraction of susceptible population

If we assume the current R0 = 2.5 but we manage to create an effective vaccine which will immunize 80% of people, Effective Reproduction Rate will be lowered to 0.5 (which is 2.5*(1-0.8)). This would mean the disease will start to decline.

However, there are a few complications when it comes to vaccination against coronavirus:

0.00 avg. rating (0% score) - 0 votes