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Herd immunity is not a good public health strategy

Universal masking, Social distancing, Personal hygiene and quality affordable care are the pillars to safe guard life against corona virus. Expecting Herd immunity to save lives is Herd mentality!

We don’t know enough about immunity to Covid-19

Covid-19: India added 100,000 cases in less than a week; tally over 500,000

A record rise of 18,552 cases in 24 hours pushed up India’s Covid tally beyond the half-a-million mark. In India, the last 100,000 cases were added in less than a week. Five states — Maharashtra, Delhi, Tamil Nadu, Gujarat, and Uttar Pradesh — account for about 67 per cent of the total cases and 80 per cent of the deaths. Bangalore has added about 800 cases just yesterday! City’s tally crosses 3000.There are 495 active containment zones.

With epidemiologists predicting a peak in July-August, the pace could continue on an upwards trajectory. India is at number four in terms of Covid cases, and eighth in terms of deaths. By now you’ve heard lots of talk about herd immunity to Covid-19 — perhaps the hope that it will be key to getting life back to some semblance of normalcy. Well not really!

The whole point is to minimize death and morbidity! If you are staring at hundreds of deaths, what good is herd immunity?

Vaccine immunity moves you, directly from susceptibility to immunity. Vaccines are usually the best way to do it because they’re designed to elicit a robust immune response.

Humans are not herds.

since the start of the coronavirus pandemic, use of the term “herd immunity” has spread almost as fast as the virus.

Trying to reach herd immunity will be a disaster. Such a strategy could cost millions of lives.

Herd immunity is community immunity. Herd immunity, which varies depending on the pathogen, is calculated based on the transmissibility of a disease — the number of people one infected person can infect!

when a large part of the population of an area is immune to a specific virus disease, majority are resistant to the cause of a disease, the virulence of such as a virus comes down drastically! While not every single individual may be immune, the group as a whole has protection. This is because there are few high-risk people overall. The infection rates drop, and the disease peters out. This is the best that can happen in the absence of specific treatment and a reliable vaccine!

We are waiting for this to happen as there is nothing else to look up to! corona has entered the community. Community immunity is not far off- hopefully!

Herd immunity protects at-risk populations. When your body is exposed to a virus, it makes antibodies to fight off the infection. When you recover, your body keeps these antibodies. Your body will defend against another infection. This is what stopped the Zika virus outbreak in Brazil.

Vaccines can also build resistance. They make your body think a virus or bacteria has infected it. You don’t get sick, but your immune system still makes protective antibodies. The next time your body meets that bacteria or virus, it’s ready to fight it off. This is what stopped polio.

When does a community reach herd immunity?

It depends on the reproduction number, or R-0. The R0 tells you the average number of people that a single person with the virus can infect. If the community has reached R-O, the community immunity has set in! We are now at R 2 or R 3. This means that one person can infect two to three other people. It also means 50% to 67% of the population would need to be resistant before herd immunity kicks in and the infection rates start to go down.

Research in UK from Nottingham university has shown that herd immunity sets in after about 47% pf the population is exposed to corona. Previous estimation was that it requires the exposure of 63% of the population From R-2 to 3 it should come down to R-0. when a large percentage of the population becomes immune to a disease, the spread of the disease slows down or stops and the chain of transmission is broken.

If 60% is the threshold for the Herd immunity to set in let us look at the numbers!

India’s population is 130 crores!

60% of this is 78 crores

50% of this is 65 crores

Say, the infection death rate is 0.5%, please calculate the numbers yourself. It’s fairly simple!

Say, the infection death rate is 2 or 3 % mortality, please calculate the numbers.

What makes the difference between 0.5% and 2 or 3 % morality is the infra structure, quality and care in the hospitals — like the ventilators, ICU care, oximeters, medical and para medical personnel!

In fact, the only disease the world — has ever overcome by reaching herd immunity is the 1918 Flu pandemic, and that killed about 50 million people worldwide.

The worry factors:

The corona virus is “novel,” or new. That means that it hasn’t infected humans before and everyone is at risk of infection. There’s no existing immunity to build on. With no vaccine to protect against COVID-19 yet, a large number of people will would catch the virus, get sick, and recover before herd immunity sets into the community! The only option is recovery, which means that majority of people catch the virus at some point. The theory behind herd immunity is that it’s not only that person who is protected from infection — they can’t transmit the disease to other people. Herd immunity protects people who are therefore the most vulnerable to serious illness.

In the absence of a vaccine to protect people against COVID-19, waiting for herd immunity to occur “is not a good public health strategy. Given the rapid rate of infections around the globe, we are looking to contain the spread of the virus by limiting person-to-person contact and urging the public to take steps to protect themselves and others.

Proactive mitigation strategies like social distancing and wearing masks flatten the curve by reducing the rate that active infections generate new cases. This delays the point at which herd immunity is reached and also reduces casualties, which should be the goal of any response strategy. For now, washing hands, wearing masks and social distancing remain the best ways to lessen the destruction of Covid-19 by flattening the curve to buy time to develop treatments and vaccines.

Without interventions Like social distancing and universal masking- 90% will get infected. With Masking and social distancing 75% will get the infection! we should not think of herd immunity as a light at the end of the tunnel- Joanna Wares, Richmond university

Ultimately, we will eventually reach herd immunity, through a vaccine, infection, or, most likely, both.

Though the infection numbers are going high we need to prevent Deaths and protect lives.

Keep the hospitals war ready. Upgrade the infrastructure. Train more medical and para medical persons. Use Telemedicine for intensive training. Invest in Health care.

Even if we aren’t able to get a vaccine, and even if we’re going to end up with 60 % of the population infected, we are learning more and more about the best way to treat people. Slowing down transmission gives researchers more time to identify better treatments, “so that ultimately when more people do get infected, they’re more likely to survive. We need to do it steadily so that we can reduce the number of deaths even if the number of infected is going up!

Dr N Prabhudev

Former Director Sri Jayadeva institute of Cardiology

Former VC of Bangalore university

Former Chairman Karnataka state Health Commission

nprabhudev@gmail.com

Former director of Sri Jayadeva Institute of Cardiology, Former VC of Bangalore University and former chairman of the Karnataka State Health Commission