Is Pakistan considering herd immunity?

Updated May 15 2020

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HYDERABAD: People ignore SOPs for social distancing while shopping for Eid at a cloth market on Tuesday as businesses reopen after the government eased the nationwide lockdown.—INP
HYDERABAD: People ignore SOPs for social distancing while shopping for Eid at a cloth market on Tuesday as businesses reopen after the government eased the nationwide lockdown.—INP

AS life returns to semi-normalcy with the easing of lockdown by the government, there is heightened concern that Pakistan may be opening up too soon and too fast and pushing policy inadvertently towards ‘herd immunity’ against Covid-19.

No government in the world has publicly supported the case for herd immunity because of the huge risk to human life it entails. The concept centers around enough people in the population – as many as 70 per cent in the case of Covid-19 – getting infected thereby building up their immunity to the virus. With an overwhelming majority having developed such immunity, the rest of the population would be much more secure and the infection would gradually fade away. In Pakistan, too, no official admits that herd immunity has been discussed as a policy option.

“Absolutely not,” says Dr Zafar Mirza, Special Assistant to the Prime Minister on Health when asked if the government was discussing herd immunity. Dr Mirza has been a leading figure in the national effort against Covid-19. “This is not government policy,” he says emphatically. “We are neither promoting herd immunity nor discussing it.”

Members of the Opposition have their worries though. On Tuesday PML-N Senator Dr Musadik Malik expressed fears on the floor of the Senate about government resigning itself to a policy of herd immunity. PPP Senator Sherry Rehman also mentioned these concerns in her speech in the Upper House.

Senior government officials say the relatively low numbers of deaths have helped them proceed with relaxation of the lockdown. One senior official says these low numbers may denote that the lockdown in the early stage was effective and suppressed the infection rate or that somehow Pakistanis have greater resistance to the infection.

These officials — while denying that the actual concept of herd immunity has been discussed in meetings — maintain that immunity will kick in sooner or later and that along with the already relatively low mortality rate will ensure the Covid-19 situation remains under control. “Everyone will get herd immunity ultimately as the virus runs its course,” says an official.

Is the government not concerned that this could be a dangerous path to tread? One official who has been looking at international trends says many countries are now slowly easing lockdowns even before the curve has flattened. “Let’s see what happens,” he says.

Does this amount to a gradual move towards herd immunity? The official argues there is some substance to the fact that countries like Pakistan may be better off opening up. Although there is no conclusive scientific proof yet, he says policymakers making Covid-19 decisions in Pakistan have noticed, for instance, that the trajectory of infections in California and Texas in the United States has remained much lower than in New York. “Both these states have warmer weather than New York,” he says. Similarly, he argues that New Delhi and Karachi have similar infection spreads, but New Delhi has a lower death rate than Karachi. “Wherever the temperatures are higher, the impact of the virus is lower,” he argues. “So we don’t as yet have a better alternative than easing the lockdown.”

In the last few weeks, the concept of herd immunity has been finding mention in the international media in the context of Covid-19 with many referring to Sweden as a country that has come closest to it. Sweden has broken away from international norms and has not instituted any formal lockdowns. It has however strongly advised its citizens to practice social distancing and asked older citizens to stay at home while clamping restrictions on access to nursing homes.

The logic of herd immunity is deceptively simple. When a person is infected with a virus, the body produces antibodies that fight off the infection and the person recovers. After the recovery, he becomes immune to the virus which means he cannot get it again and cannot infect any other person. If 70 per cent of the population of a country therefore is infected with the virus, the remaining 30 per cent will have very low probability of getting infected. This is because the 70 per cent who are infected and recover are not passing on the infection. The country as a whole – or as a herd – has overpowered the virus through its immune system.

The antibodies that our bodies need to fight off the infection are developed through two ways: (i) by getting the infection and allowing our body to develop antibodies naturally; (ii) through vaccination whenever the vaccine is developed.

In real life, the logic gets a bit complex. The World Health Organisation (WHO) said in a statement last month: “There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.” This means the concept of herd immunity is not guaranteed (so far) even if 70 per cent of the population were to get infected. In addition, when 70 per cent of a population gets infected, many will die when the infection overpowers the antibodies. How many may die depends on the mortality rate of the country from Covid-19.

If we apply numbers to Pakistan’s case, the situation gets clearer. At present, the country’s population stands at 220,892,340 people. Seventy per cent of this population (that requires to be infected for herd immunity) comes to 154,624,638. In other words, more than fifteen crore Pakistanis will require to be infected with Covid-19 before herd immunity kicks in.

Now let’s take this further. The current mortality rate of Pakistan as per government figures is 2.2 per cent. This denotes the percentage of people dying from among all those infected. But there is a complication. The actual mortality rate will be lower because the confirmed cases of infections that we have is far less than what the actual number of infected people are. Since our testing numbers are low it is difficult to get a fairly accurate assessment of the total number of infected citizens.

“Every identified case represents the tip of the iceberg,” says Dr Mirza. He argues – rightly so – that science does not allow us to make an accurate estimate.

However, projections require some projected data. According to an infectious diseases specialist, the actual figure of infections in Pakistan could be anywhere from double the confirmed figure to ten times upwards. This provides us a wide range to apply on the concept of herd immunity. Since the current mortality rate of the confirmed infections is 2.2 per cent, doubling the number of infected cases would bring down the projected mortality rate to 1.1 per cent. If we increase the actual cases ten times, the mortality rate would reduce by ten times and end up at a figure of 0.22 per cent. Therefore, the range to apply to the herd immunity level would be 0.22-1.00 per cent.

If 0.22 per cent of Pakistanis were to die by the time the country reached the 70 per cent infected population for herd immunity, the death toll would be 340,174.20 (0.22 per cent of 154,624,638). If 1.00 per cent mortality rate were applied (1.00 per cent if 154,624,638), the number of people dead would be 1,546,246.

These projected numbers are rough approximations that do not include multiple factors that go into scientific projections. But they do provide a crude picture of what the concept of herd immunity entails in cost of human lives.

Medical experts agree that at some point we will all acquire herd immunity like we have done so with diseases like measles, mumps, chickenpox and polio (though we in Pakistan are struggling with polio). The issue is time. If a population races towards herd immunity before a vaccine is available, the cost in human lives can be catastrophic. This is why, experts say, the aim is to suppress the spread of infection so that the health facilities are not overwhelmed before a vaccine is made available.

“I care less about herd immunity and more about our hospitals coping with the pressure on patients,” says Taimur Saleem Jhagra, the health minister of Khyber Pakhtunkhwa. Jhagra is leading his province’s fight against Covid-19 and is widely credited for his pro-active and data-oriented approach to the challenge. He says more important than the number of infected people is the number of those needing hospitalisation. The death rate climbs in proportion to those needing hospitalisation. If health facilities are overwhelmed, death rates could spike beyond control.

But so far the government feels it has the situation under control.

“Our health facilities are coping well,” says an official associated with National Command and Operations Centre (NCOC). According to data from NCOC, Pakistan today has a capacity of 21,000 hospital beds dedicated for Covid-19 patients. The number of Covid-19 patients currently hospitalised is 6661. The total number of ventilators currently available for treating Covid-19 patients is 1,400. As of today, 93 patients are on ventilators. There is excess capacity. For now.

Dr Mirza says the global average for people on ventilators is 4.8 per cent while in Pakistan currently it is 2.5 per cent. These numbers have given officials like him and Jhagra cause for cautious optimism. But how long before red lights start flashing?

Almost all officials agree that the next two to four weeks are crucial because they will reflect the outcome of the decision to ease the lockdown. One senior official says the impact of opening up mosques for Ramazan will become fairly clear by Eid. The result of easing the lockdown earlier this week will manifest itself by the second week of June. There is concern that widespread violations of laid down SOPs for social distancing – as seen in the last two days – could lead to dangerously escalating pressure on health facilities.

“If hospitals are suddenly overrun, we will be in trouble,” admits another official who is tracking numbers. “If more than 75 per cent of hospital beds are required for Covid-19 patients we could face a serious crisis,” he says.

A senior member of the government who attends NCOC meetings airs similar concerns. He argues that so far the real data of infections and deaths has been lower than the projected figures. “If in the next few weeks, these real figures start to go beyond the projected values then we shall be in a dangerous situation,” he says.

The government could be skating on thin ice. As could Pakistan.

Published in Dawn, May 13th, 2020