Monday | 7 October 2024 | Reg No- 06
বাংলা
   
Monday | 7 October 2024 | Epaper

“Variants always become less virulent” can be misleading

Published : Thursday, 10 March, 2022 at 12:00 AM  Count : 802
ZUBAIR KHALED HUQ
Are we cautious that the pandemics far from over, is it not too early to be complacent? Are we going back to square zero, with decreasing trend in transmission we are not permanently relieved from newer strains? New variants will emerge and such variants could be more transmissible than the Omicron BA.2 variant. The next variant of concern may be more aggressive, and it may be more transmissible because it will have to overtake what is currently circulating. The big question is whether or not future variants will be more or less severe, evading antibodies.  

The only way the next variant can become even more transmissible than the Omicron variant is by exhibiting a far higher ability to evade neutralising antibodies. This would mean that full vaccinations will be even less effective in preventing breakthrough infections. But so far, fully vaccinated people have been found to be less likely to suffer from severe disease requiring hospitalisation and even death. That is because it is the T cells and B cells that come into play to reduce the severity of the disease. The memory T cells are extremely unlikely to prevent SARS-CoV-2 infections. That is just not what cells generally do. They may reduce COVID-19 disease severity and prevent deaths.    

Virulence is totally unpredictable, while the next variant has to necessarily be more infectious than the Omicron variant, whether the variant will be more or less severe cannot be said with certainty. But it is important to remember that right from the very early stage of the pandemic, it became clear that transmission or virus spread begins even before symptoms can show up. That is what makes the virus tricky. Since transmission begins even before symptoms set in and well before the disease becomes severe, it can be a silent intruder. As a result, the natural evolution process selects variants not based on how they cause disease but how they can escape neutralising antibodies.

Almost all SARS-CoV-2 transmission happens while people have no or few symptoms, there is no particular reason for severity to play a role in evolutionary selection. Immune escape mechanism is the tricky part: the virus was novel and none in the world had any immunity in the beginning of the pandemic. But with millions being infected by the virus and millions being fully vaccinated, and some with a combination of natural infection and vaccination, the next variant has to necessarily exhibit higher immune escape to cause infection.

This is the reason that the next variant will exhibit more immune escape than the Omicron variant. Even though the Omicron variant caused a large number of infections in those who have been previously infected and vaccinated, at the population level, disease severity has been far less severe compared with the Delta variant. But lower disease severity was seen more in people who have pre-existing immunity either from vaccination or previous infection.  

Two studies that tried to document the intrinsic disease severity of the Omicron variant compared it with the Delta variant. The studies found that the Omicron variant is about 75% as likely to cause severe disease or death as the delta variant. In the Omicron-driven wave, severe COVID-19 outcomes were reduced mostly due to protection conferred by prior infection and vaccination, but intrinsically reduced virulence may account for an approximately 25%reduced risk of severe hospitalization or death compared to Delta.  

In the second study, a report by the Imperial College COVID-19 response team found 69% reduction in hospitalisation risk in people who have been re-infected compared with primary cases. Viruses don't inevitably evolve toward being less virulent; evolution simply selects those that excel at multiplying. Delta was more severe than Alpha which was more severe than the original virus. Omicron is milder than Delta but likely not milder than the original virus.

There is a saying that time is the greatest healer, but only with the right use of time. We have to be fully protected not only by getting vaccinated, but by protecting ourselves by mask also. Why should one fight inside one's body if the intruder is kept at bay? Not allowing entry is far better than changing your strength, luck and antibody efficiency. Using herd immunity as the saviour is good. Herd immunity also can be reached when enough people have been vaccinated against a disease and have developed protective antibodies against future infection. Unlike the natural infection method, vaccines create immunity without causing illness or resulting complications.

We have seen mass vaccination programmes to be successful. Using the concept of herd immunity, vaccines have successfully controlled contagious diseases such as smallpox, polio, diphtheria, rubella and many others. Herd immunity makes it possible to protect the population from a disease, including those who can't be vaccinated, such as new-borns or those who have compromised immune systems. It is a great pleasure we are moving towards that, but the question is we sure to be protected by that from newer variants. Time will only say, the path we have to take.

Vaccine hesitancy and reservations can make some people may object to getting a COVID-19 vaccine because of fears about the possible risks or scepticism about the benefits. If the proportion of vaccinated people in a community is below the herd immunity threshold, a contagious disease could continue to spread. We are waiting for approval from WHO for vaccinating children below twelve years, if it comes into play sooner than later could go a long way for attaining herd immunity. Our mass vaccination program could be more fruitful.  

About the protection the vaccine gives ids the burning question. It's not clear how long the COVID-19 vaccines will protect you. Further research is needed to see how much the COVID-19 vaccines reduce transmission of the COVID-19 virus. Also, research suggests that COVID-19 vaccines may have lower efficacy against some of the variants of the COVID-19 virus. New variants, which could be more resistant to vaccines, are regularly emerging. The distribution of the vaccines has greatly varied among and within countries. If one community achieves a high vaccination rate and surrounding areas don't, outbreaks can occur if the populations mix. World leaders should make sure that vaccine roll out are inclusive and equally distributive, irrespective of their economic or political status.    

According to the CDC, if you are vaccinated, you can more safely return to many activities you may not have been able to do because of the pandemic. However, if you are in an area with a high number of people with COVID-19 in the hospital and new COVID-19 cases, the CDC recommends wearing a mask in public. Mask wearing has to be mandatory for all outside even if we are operating fully in all areas.   Continued virus survival, spread and virulence are all about the evolutionary pressures of multiple factors, including the number of people available to infect, how long humans live after infection, the immune system response and time between infection and symptom onset. Unfortunately, that means it's nearly impossible to predict the future of the pandemic, because viruses don't always evolve in a predictable pattern.                                                                                                                            
Dr Zubair Khaled Huq, Family Medicine, Gerontology, Public Health Specialist








LATEST NEWS
MOST READ
Also read
Omicron BF.7
2022 stories that could still have an impact on our lives
Dealing environment with data
Foreign interference in internal affairs
Management factor in our health sector
Diplomatic norms and code of conduct through the lens of international law
Dealing air pollution in winter
Germany to suspend humanitarian aid for Afghanistan
Editor : Iqbal Sobhan Chowdhury
Published by the Editor on behalf of the Observer Ltd. from Globe Printers, 24/A, New Eskaton Road, Ramna, Dhaka.
Editorial, News and Commercial Offices : Aziz Bhaban (2nd floor), 93, Motijheel C/A, Dhaka-1000.
Phone: PABX- 41053001-06; Online: 41053014; Advertisement: 41053012.
E-mail: info©dailyobserverbd.com, news©dailyobserverbd.com, advertisement©dailyobserverbd.com, For Online Edition: mailobserverbd©gmail.com
🔝