Hidoc Bulletin

All sectors of the present human lifecycle are immensely affected by sudden COVID-19 waves. This started the massive vaccination drive among a larger population in order to boost immunity & regain normalcy. 

What is herd immunity?

It is indirect protection, community immunity, or shielding achieved by immunizing an adequately large percentage of the population against an infection. Herd immunity decreases the epidemic’s threat, offers disease resistance, reduces the chances of infected individuals & susceptible individuals contact & hinders infection spread. For individuals who are difficult to be vaccinated like new-born & people with compromised immunity, herd immunity provides infection defence.  

 How does herd immunity happen?

It can be acquired in 2 ways. 
Infection- This occurs post-infection exposure leading to the development of protective antibodies & natural immunity during the recovery period. 

Vaccination- This is done by vaccinating the majority of the population & building immunity without causing the real infection. Usefulness is determined by vaccine effectiveness in transmission reduction, target pathogen transmissibility & achievable vaccine coverage population. 

What is the herd immunity threshold (HIT)? 

Percentage of disease-immune people that are notably responsible for decreasing sequential infection spread. 
It is calculated as 1-1/R0, where R0 is a critical variable. In an immunologically susceptible population, R0 is the average number of secondary cases caused by infected individuals Social and demographic elements such as population density, public health measures, & cultural attitudes and behaviours impact R0, inevitably resulting in noticeable disparity in HIT predictions.

Disease transfer continues if in case the proportion of vaccinated people evaluated is below the calculated HIT. 

What are the hurdles of herd immunity?

• Vaccine hesitancy due to religious objections, fears & mistrust about the vaccine benefits

• Questionable vaccine protection & unclarity about immunity towards new variants  • Uneven vaccine launch, distribution & frequent infection outbreaks 

 • Distress of vaccine-related complications like soreness, swelling, fever & rashes

Herd immunity & its crucial facts

A sufficient HIT cannot be achieved in countries with low seroprevalence even after finishing all adult vaccination, if there is a high number of children population, although infection impact can be reduced among high-risk populations. 

SARS-CoV-2 control should not only be predicted by considering herd immunity as an accurate biological parameter.

Along with herd immunity-focused pandemic controlling tools should be utilized to diminish viral movement-related illness.

Strengthening herd immunity will surely decrease infection likelihood, reinfection & hospitalization. 

Vaccination, completing required doses along with booster doses & restricting virus mutation decides the timespan to secure herd immunity. 

Vaccine update & alternative treatment development relies on the steady sustained global examination & investigation of COVID-19 variants. This will prevent emerging new variants associated with herd immunity decline & infection risk to the unvaccinated populations which may lead to alarming illnesses.

Conclusion 

Accomplishing herd immunity is difficult & demanding. It requires worldwide immunization campaigning, mass vaccine-related awareness & distinct vaccine administration.