Prof. Malavige tackles vaccine-related concerns
Many are concerned over a few vaccinated people (either with one dose or both doses of AstraZeneca’s COVISHIELD) being infected by COVID-19. The Sunday Times raised these concerns with Prof. Neelika Malavige, Head of the Department of Immunology and Molecular Medicine, University of Sri Jayewardenepura. Can people get infected with the virus, even after taking the vaccine?
Yes, the efficacy of different COVID-19 vaccines is about 70 to 95% (depending on the vaccine). This is after taking both doses and about three weeks have lapsed after the second dose.
This means that after both doses about 5-30% of the people (if 100 have taken the vaccine, 5-30 people) could get COVID-19, but with no symptoms (asymptomatic) or very mild symptoms. They would have reduced severity of the disease and not face death.
The efficacy of a vaccine, in this instance, means its ability to prevent a symptomatic infection by the disease-causing bug (SARS-CoV-2). Therefore, those who receive these vaccines can have asymptomatic or very mild infection. They can also transmit the virus to others. However, generally, the amount of viruses in their respiratory secretions is very much less than non-vaccinated people.
So, fully vaccinated people are less likely to transmit the virus than unvaccinated people. When the WHO evaluates the vaccines before giving approval, it looks at the efficacy of the vaccine in preventing symptomatic infection, severe infection and death.
It is important to note that these vaccines cannot be used to prevent transmission of the virus. To prevent transmission, a large proportion of people (at least more than 75%) should be vaccinated.
Can vaccination eradicate COVID-19?
No, vaccination cannot eradicate the disease. Vaccines that completely prevent infection can eradicate infection, but none of the COVID-19 vaccines can achieve this. However, if 70-80% of the population of a country is vaccinated, it can reduce severe disease and death in the vulnerable population.
This may lead to a situation where even if people get infected ( after the vaccine), it would be like getting a cold. But at this point of time, such a scenario is definitely not possible. Therefore, until we can vaccinate a large proportion of the population, all of us have to follow the health guidelines strictly.
You might be fully vaccinated but become asymptomatically-infected and then infect the unvaccinated people in your house. Therefore, it is important to be aware of this. The vaccines ONLY protect the individual who received the vaccine. Can new pandemics be possible over and over again as the world faces ‘variants of concern’ such as the United Kingdom (UK) variant, the Brazilian variant, the South African variant, the double-mutant Indian variant and a mix of two (UK and Indian variants) as found in Vietnam?
If the examples of the UK and the United States of America (USA) can be cited, more than 50% of their adult population has been fully vaccinated (taken both doses), while the balance 50% have taken the first dose. So, even if a large population gets infected with new variants of the virus, there would be less severe disease and no deaths. This would be like influenza. Every year, new influenza variants emerge. Many people get infected and some develop the flu. Yearly vaccines (flu shots) are given to individuals who are likely to develop severe disease, with the influenza virus. Is it better to take at least one dose of a vaccine? Except for a few COVID-19 vaccines, all others are twodose vaccines. For the twodose vaccines, only both doses give complete protection. The efficacy of one dose is only known for the AstraZeneca and Pfizer vaccines.
In a situation where there are very limited vaccines, it is better to take at least one dose, as some immunity is better than none. Some immunity will prevent severe disease and death in most individuals. One dose of AstraZeneca’s COVISHIELD or Pfizer did reduce severe disease in other countries within the first three months, following the single dose.
The ideal situation, however, would be both doses. But better one dose than no dose. If there is a person who is starving, it would be good to give that person a slice of bread, rather than waiting to provide two slices.