It has been over two years since we have been able to go out with a light heart, carefree mind and have some pleasant time with family and friends. Or visit a pagoda, monastery and sacred places to worship or carry out some good deeds. Wearing masks, avoiding crowded places, keeping a distance (6’) from other people, washing hands frequently have all become the new normal for us. The emergence of Covid 19 came at a time when information traveled very fast and as the incidence of infection picked up and death rates increased especially in aged persons and those with pre-existing diseases (co-morbidity) the public became alarmed and observed the suggested health related behavior quite readily. Nearly all infected persons went into quarantine without complaint. Many people took their Covid vaccinations willingly even though there were some who did not – because they were not willing to take it or because the vaccine was not available. The disease incidence and death rates decreased gradually so that by early 2022 people became lax in following disease prevention measures.
This decline in incidence and deaths may be attributed to many factors. One important factor may be the development of ‘herd immunity’. The term, as stated by Fine, Eames and Heymann1, applies to the decline in the risk of infection in susceptible individuals by the presence of and proximity to immune individuals. It is unclear how much or what percentage of the population should be immune (due to vaccination or overt disease) for herd immunity to play a significant role in disease reduction. In practical terms what percentage of the population should be vaccinated for herd immunity to appear? Some mathematical formulae have being proposed by epidemiologists to find out the threshold level of immune persons in the population above which the incidence of infection will decline. Once the threshold level, e.g., the percentage of population that should be vaccinated, has been identified health personnel should try to achieve that target. On the other hand, herd immunity may be hard to attain in case of Covid-19 as the virus keep coming out with many variants which are not protected by vaccines produced with different variant prevailing at the time. Also, the vaccine as stated below does not prevent reinfection or prevent transmission of disease to others. It seems the vaccines were not blocking transmission of infection.
The recent increase in incidence of Covid cases can be attributed to many factors – on the part of the general population and also to changes in the virus itself. The population as stated above became lax in undertaking disease prevention measures; not wearing masks, not washing hands, going to crowded places, not practising social distancing which was observed during the early stages of the outbreak. They also thought they would be protected from getting infected after getting vaccinated. The vaccine appears to be effective in preventing symptomatic disease, reducing mortality but unclear whether it will prevent infection or transmission of disease to others by the infected person. On the part of the virus, it is only natural that they have to mutate, change, becoming different variants for their survival. The latest variants of Covid is said to be BA4 and BA5, against which there appeared to be no protection from the vaccines available at present.
It is possible that Covid will become endemic like influenza. From the clinical picture we are seeing with Covid variant BA4 and BA5, they appeared to be more infectious but less virulent. The severe effects are seen more in elderly persons and those with co-morbidity, underlying diseases. As health personnel we can advocate the public to follow the Covid preventive measures which can be seen on most social media platforms quite strictly again. We have to learn to live with Covid as we have done with influenza.
Reference
- Fine P, Eames K and Heymann DL 2011. “Herd Immunity”: A Rough Guide. Clinical Infectious Diseases 52(7): 911-916 Downloaded from https://academic.oup.com/cid/ article/ 52/7/911/299077 on 17October 2020 (forwarded by Dr. Ye Hla)
