Corona epidemic : Herd immunity not yet decided due to decreasing effect of new forms, vaccines


To overcome the corona epidemic, measures are being taken to generate herd immunity from vaccines around the world. In such a situation, many people are curious to know that by vaccinating how much population we can achieve the goal of herd immunity. So that the lockdown ends and everyone starts living their life without fear. Travel around the country and abroad and spend free time with your loved ones.

According to Professor Julie Lisk of the University of Sydney and James Wood of the Public Health Academic, UNSW, there are three major reasons behind this, which are important to understand.

1) Changing nature of epidemics and differences in vaccines

It is difficult to predict herd immunity in the case of a virus-like the rapidly changing corona. The infectiousness of a disease is understood by the RO i.e. the speed of its progression.

If we look at the corona, the RO of its original form is two to three, but the transition of the delta form is twice that and its RO is around four to six. Its type, dosage of vaccines, and the effect of their different types also matter a lot.

Data from the UK showed that two doses of the Pfizer vaccine are between 85 and 95 percent effective against the alpha variant, while two doses of AstraZeneca are 70 to 85 percent effective.

There has been a decline in the effectiveness of vaccines for the delta form by about ten percent. That is, the lesser the effect of vaccines against new forms of the corona, we will need to have more vaccines for herd immunity.

2) It is not possible to vaccinate the entire population right now

Take the example of Australia, there has now been provisional approval to vaccinate children aged 12 to 15 years. It will take a long time to get them vaccinated, even if routine approval is given for this age group.

Even if this happens, the gap in the safety of young children will remain. Therefore, children should benefit to some extent from the same vaccinations as adults. For example, 48.5 percent of people in the UK have had both doses. Initially, there was a decline in infections among children under the age of ten. This was partly possible due to the protection provided to adults.

3) Collective defense will vary depending on the time and place

The efficacy of existing vaccines will wear off over a period of time. With the advent of new forms of the corona, we will definitely need a booster dose.

We rarely speak of mass immunity with influenza vaccination, as the duration of protection from these vaccines is very short. At the same time, protection against these viruses can also vary from region to population. Herd immunity also depends on population density.

With these factors in mind, experts often avoid giving fixed figures for collective immunity. Especially given the contagion of Delta, we have to increase the vaccination rate much faster. Only after that life will start looking a bit normal. However, outbreaks of corona will keep coming but then they will be less risky.