1. How important is herd immunity.
Vaccines train our bodies to produce antibodies that will protect us from getting the disease. It also prevents us from transmitting the disease. Both of these will break the chain of transmission. If we can immunize a certain proportion of the population, we will be able to prevent others who are not immunized due to various reasons eg children less than 12 years old, allergy to the vaccine, those who refuse the vaccine.
2. How big a role does it play in reducing transmission of the Covid-19 virus.
For measles this threshold (herd immunity) is 95%. The remaining unvaccinated 5% will be protected since measles will not spread due to the population immunity. For polio, it is about 80%. The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not yet known.
According to modeling studies in Imperial College London, a vaccine that is 90% effective at blocking viral transmission (like mRNA vaccines); the herd immunity effect will be achieved at 55%, with masking and physical distancing in place. If masking and physical distancing is lifted, 67% coverage of the population is required.
If the vaccine is less than 90% effective at blocking viral transmission or we are faced with the transmissible Delta variant, then the vaccine coverage must be greater to stop of the circulation of the virus.
3. Should we place great emphasis on achieving herd immunity.
We should not be trapped in the polemics of herd immunity. I think it is important to ramp our vaccines speedily and widely to the best of our capability and protect as many of our rakyat from severe covid which would lead to hospitalisations and deaths. However, we are utilizing covid vaccines with variable vaccine effectiveness and different capabilities of preventing the transmission of the virus. The faster we vaccinate and the wider the coverage of our program than the more people will be protected directly, and will confer indirect protection (ie herd immunity) to those who have yet to receive the vaccine or are unable to be immunized due to various reasons.
4. If more than 80% of the population is vaccinated can life return to normal.
Most certainly, back to near normal. The best example is Israel where 60% of the population have been fully vaccinated with mRNA vaccines (Pfizer and Moderna). Previously, the Green Pass and Purple Badge systems set guidelines as to who can enter public venues and how those venues can operate They have lifted this mandate, so Israelis no longer require proof of vaccination or covid recovery to enter any venue and there is no more any capacity limits at stores, restaurants etc. There are now no caps on gatherings, indoors or outdoors.
Most businesses and schools have returned to normal. However, masks are still required for indoor activities. This is expected to be lifted soon. Early in January, Israel recorded 8,000 cases per day, it is now less than 30 daily cases.
5. Will we have to live with the Covid virus just as we have to with influenza
First thing we must stop doing is comparing covid with the flu. They are 2 different viruses, the influenza virus and the coronavirus. The Ro (Reproduction Number) of the flu is 1.3 whilst the CoV (coronavirus) is 2-3 and the Delta variant maybe 6-8. Which means for the transmissible Delta variant, 1 person may spread it to 6-8 other persons. The hospitalization rate of the flu is 2% whilst 20% of covid patients needs to be hospitalized. The deaths rates are higher with covid, the case fatality rate being 1-3.4% compared to less than 0.1% with the flu.
6. How important is a booster shot for those who have been vaccinated.
Upon being infected with covid, the body has 3 major immune responses:
- Cytotoxic T cells which eliminate infected cells
- Neutralizing antibodies which prevents the coronavirus from infecting cells
- Memory plasma cells which remains for a long time, if not a lifetime, in the bone marrow. They are triggered into action, when attacked by the coronavirus or when given a vaccine.
Researchers have detected these plasma cells after 1 year of covid infection, suggesting long term immune protection.
By giving a vaccine, the antibodies are boosted by 50 times, some of which are recruited as memory plasma cells.
*This article was published in The Sun: https://ipaper.thesundaily.my/epaper/viewer.aspx?publication=The%20Sun%20Daily#page/4
