Interesting Factoids: COVID. Is it as lethal as people make it out to be?

A black thread of fear has permeated the entire fabric of human life. We are now in the After COVID (A.C.) era. Try as we may, it is difficult now to even imagine going back to B.C. (Before COVID) times!.

Is the fear of COVID justified? Or is this all media hype?

Antibody studies carried out in some parts of the world, have suggested that prevalence of COVID is 50–80 times of what was previously thought. In layman terms this means that, if in a particular area there are 100 people tested to be positive, in reality there are 5000–8000 asymptomatic infected individuals who don’t even know that they have been infected! By the way, this is actually good news, NOT bad!

Reason?- this actually brings down the mortality (death rate) estimates for the disease from around 3%, to around 0.12–0.2%. So basically instead of 3 out of 100 infected people presumed to die (as is currently thought), only 1–2 out of 1000 infected people are actually seriously ill or dying/ dead!

Optimists argue that this doesn’t actually seem like a big number at all, considering that mortality from tuberculosis (TB) is around 3% i.e. 3 out of 100 people infected with TB, die from the disease! In India it is estimated that around 2,20,000 deaths are reported due to tuberculosis every year. And yet, we don’t panic about TB as much!. COVID only kills 1–2 people out of every 1000 infected. Why are we panicking so much about COVID, when we don’t get mortified by TB, which is 10 times as lethal???

Well, that is not the way to look at it. When estimating the severity of a disease, there are two prime factors to be considered:

1. R0: This refers to the number of people that a single infected person can transmit the infection to. The disease with the highest R0 is measles (around 16, i.e. one infected person infects 16 others- hence the aggressive vaccination program for measles). In the initial stages where restrictions/ lockdown were not imposed, corona virus had a R0 or nearly 5–6, i.e. one person was infecting nearly 5–6 other people (this is how the virus spread so quickly after the Tablighi Jamaat meeting)!.
2. Serial Interval: This is the average time between each successive infection. Some studies estimate the serial interval of Corona virus at 4 to 4.5 days. This basically means that it takes 4–5 days for a patient to spread the infection to another individual.

So, both these factors are necessary to determine the severity of an infection. If we take the example of Corona virus: with an R0 of 4–6 and serial interval of 4–5 days, each infected person infects an average of 5 people, every 5 days. So by day 5, one person would have infected 5 people. These 5 people would have each infected another 5 people by the 10th day (total infected = 5x5=25). By the 15th day these 25 would have infected another 5 each= 25x5=125 infected people!

To put things into perspective, Spanish Flu which is estimated to have wiped out nearly 5% of India’s population in 1918–19, had an R0 of 2 and a serial interval similar to COVID. So essentially Corona is infecting twice as many people as the virus which wiped out 12–17 million people in India alone, a century ago!.

How does social distancing/ lockdown help? Social distancing reduces the possibility of one person transmitting the infection to another. With social distancing now imposed, in India the R0 for coronavirus has come down to around 1.5. So basically by day 5, only 1.5 people are infected, by day 10- 2 people and, by day 15 approximately only 3 people are infected, instead of 125!

So how do we compare this to TB? Though the R0 of TB is difficult to accurately estimate due to its relatively varying prevalence based on country to country (0.24–4.3), the serial interval is very low at around 1 year or 365 days!! . So one TB patient will only infect another patient after 1 year!!! Thus, the prevalence or the number of people affected by TB at any given time is only 0.5%. i.e only 5 out of 1000 people in the general population are infected. Therefore, say in a population of 100000 people one expects 500 TB infected individuals. Of these 500 people, around 3%, i.e.9 people are expected to die. So in that population of 100000, only 9 people die from TB. Now, consider the same population infected with COVID. Nearly 100% of individuals are expected to contract the Corona virus within a year, based on our R0 and serial interval calculations as above, as it is believed to infect almost everyone that come into contact with it. If we presume a mortality of 0.2% (discussed above), then we can expect around 200 deaths in a population of 100000, nearly 20 times that of TB. What is worse, is that these deaths would happen within a short span and overwhelm the system, because it’s not just the deaths; for every person dead, we would expect to have 4–5 other sick people who may need hospitalisation. So, in a city the size of Visakhapatnam with a population of 30x 100000, we can expect 6000 deaths, with 30000 people needing hospitalisation. Considering the fact that these patients would have blocked the beds for patients with heart disease, stroke, TB etc who would also need treatment simultaneously, this is not something we would be able to cope with!

That is why we are (and should be) terrified of COVID and continue social distancing, till we are able to reduce the R0 to negligible levels, near zero!

This now brings me to the prevention part of it!

How does a vaccine help? Why is a vaccine expected to take more than 1 year to come about?

The picture below gives a summary of what the vaccine development process involves and where we are currently.

How effective can we expect the vaccine to be?

If a future COVID vaccine has to be trialed on unaffected individuals and shown to be significantly effective in preventing severe infection/ death, it should at least be as effective as the current seasonal flu (influenza) vaccine, the closest comparable viral infection.

How effective is the current seasonal flu/ influenza vaccine?What can we learn from the seasonal flu vaccine?

The current mortality estimate of seasonal flu is 0.1% (slightly lower than the revised COVID mortality estimate of 0.2%) i.e. 1/ 1000 patients infected die. Seasonal flu vaccination programs around the world are believed to reduce mortality by 50%. So, once vaccinated, instead of 1 in 1000, 1 in 2000 infected patients die. Even though that doesn’t appear much- it is considered a 50% reduction in mortality and that is a considered a good result, considering that on the whole it also reduces the number of flu related hospital admissions. Public Health England estimates that on average 17,000 people have died from the flu in England annually in the recent past, despite the presence of an active vaccination program. So without the vaccine, England would have had 17000 more deaths per annum.

Coming back to the Corona vaccine- given our previous experience with the influenza vaccine, realistically one cannot expect the corona vaccine to be 100% effective in preventing infection. Similar to Influenza vaccine, one may expect a 50% reduction in hospital admissions and deaths, i.e. it should reduce the mortality from the current 2 in 1000 infected patients, to 1 in 1000. Though this does not sound significant, remember that it would also reduce the R0 from 5–6, to 2–3 people. Further, the serial interval would also increase from 4–5 days to around 8–10 days, as vaccinated people would also be a bit more immune to getting the virus infection. Thus by day ten, one would expect only around 2–3 people being infected, in contrast to 25 people (see calculation earlier) that would have been infected, without vaccination. This is a significant result!

However vaccination studies take time as nearly 20–30 thousand people need to be studied in order to ascertain whether the vaccine really works. This is simply because 80–90% of these people would not develop any symptoms of the disease even without the vaccine anyway and we need to make sure that any reduction in disease related deaths/ hospital admissions in the trial, is not simply due to chance! We also need to make sure that the vaccine is safe with relatively few side effects. Moreover, remember that the virus keeps mutating. Around 11 strains of Corona (SARS-CoV-2) have been identified so far. Luckily the strains are not significantly different from each other and any vaccine should hopefully work against all current strains. However, there is no guarantee that in another 6–12 months, the mutations would be significantly different, making the vaccine developed against the current strains ineffective!

Thus, despite the vaccine, one may still expect a version of COVID to linger on like seasonal flu, and continue to take lives seasonally. The vaccine therefore is not going to end our tryst with COVID, but hopefully significantly reduce the disease burden.

On the brighter side, the chances of one dying from COVID are still quite low considering that it kills only 1–2 out of 1000 people infected. This is no reason to rejoice, but given that a vaccine is still many months away, it is reason enough to probably get on with our lives, in a controlled manner, while continuing to maintain as much social distancing as practically possible.

What about Treatment for the disease? Surely some drug is going to help to treat the disease?

Well, we should remember that only around 2–5 out of 100 patients with the infection actually need treatment. The rest would have minimal or no symptoms at all and would recover regardless. Out of these 2–5, the majority are elderly and people with other diseases (comorbidities). These people would be at high risk anyway. We are yet to know the exact mechanism by which Corona kills the patient. Surely there may be some drug that may help reduce the number of deaths, but one cannot expect the treatment to produce miracles. So I wouldn’t hold my breath on it!

We are at a very interesting point in human history. Let us all hope we continue our social distancing protocols and manage to see and experience a good part of the after COVID years. Testing times ahead!…………….