Mass vaccination programs are currently rolled out in almost every country in the world to prevent the unrestricted spread of Covid-19 disease. The aim is to achieve herd immunity where a large proportion of population is immunized against the threat of the infectious disease. Many nations have successfully implemented mass vaccination programs in the past when battling pandemic disease like small pox that killed millions of people in the world for nearly two centuries.
WHO, World Health Organization defined herd immunity as the immunization status of the population where indirect protection from disease is achieved when population is immune either through vaccination or through immune status developed through previous infection. The best possible way to achieve herd immunity is through mass vaccination and not through allowing unchecked disease spread which could result in unwanted human loss and suffering.
Immunization status achieved through Covid-19 mass vaccination program allows individuals to develop protective antibodies in a similar manner achieved when exposed to disease but with the advantage of not falling sick. Both vaccinated individuals as well as individuals who contracted disease previously particularly covid-19 disease would have developed these protective antibodies that can fight the Covid-19 disease. Many nations delayed their mass vaccination programs due to poor understanding by their ruling leaders of the protection afforded by the vaccination by preventing sickness associated with contracted disease.
It is not yet clearly defined what proportion of population that needs to be immunized to achieve the herd immunity against covid-19 disease. There is varying levels of emerging evidence attempting to answer this hard question. In the past , herd immunity was achieved against diseases like polio through eighty percent immunization status of the affected population and against measles through ninety five percent immunization status of the affected population.
Most of the countries are currently securing vaccine stocks manufactured by multinational pharmaceutical giants like Astrazeneca, Pfizer, Moderna, Johnson & Johnson, Novamax as well as national pharmaceuticals like Sinopharm in China and Gamaleya National Centre in Russia and Serum Institute of India. However, many developed nations including Australia and New Zealand as well as developing nations like India, China and South Africa are way behind in achieving their mass vaccination targets required to achieve her immunity. Currently the global vaccination status is around 28%, where at least one vaccine dose was received per person.
There are many barriers to successful implementation of vaccination at this stage. Some of them are related to procurement of vaccines. The other factors include the changing landscape regarding the evidence of efficiency of current vaccines against emerging variants of covid-19 virus. Many of the existing vaccines are shown to achieve protective immunity against all the variants of covid-19 virus. Many clinical research studies are being conducted across the world to broaden the evidence base which will help the world in better preparation for achieving herd immunity.
In the mean time many nations have either continued their lock down status or implemented new lock downs to prevent the covid-19 disease surges due to new variants. While lock downs and other restrictive measures like border closures may help in preventing rapid spread of the covid-19 disease during surges, the safest bet against the spread of current covid-19 pandemic is to achieve herd immunity through safe and effective vaccines. Mass vaccination can help in making the covid-19 disease rare and save lives across the world.