Coronavirus: what if vaccines aren’t enough for herd immunity?
- Production problems for Pfizer-BioNTech and AstraZeneca give an inkling of the difficulties ahead as countries try to vaccinate their way to freedom
- Some experts warn it is ‘wholly unrealistic’ to expect herd immunity in the foreseeable future. Others say Covid-19 may never be eradicated
The grim milestones of 100 million infections and 2 million deaths may have been passed, but along with the vaccines comes the hope of herd immunity, a future world in which Covid-19 has been slowly throttled out of existence as it runs out of hosts to infect.
Or at least that’s one rosy scenario. Unfortunately, experts are warning it may be a little too rosy.
Another scenario, offered by Mike Ryan, head of the World Health Organization’s (WHO) emergencies programme, is that vaccine coverage will not be enough to stop transmission of the virus, at least not for the “foreseeable future”. Some experts go even further, cautioning the virus may never be eradicated.
The “bar for success” according to Ryan, is not herd immunity but “reducing the capacity of this virus to kill, to put people in hospital, to destroy our economic and social lives”.
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Production and distribution delays at major vaccine producers including Pfizer-BioNTech and AstraZeneca, along with the news the European Union is considering tightening export restrictions on vaccines made in the bloc, have raised concerns over whether even the world’s richest countries will meet their vaccination targets. The European Union, Canada and Singapore were all hit by Pfizer’s announcement that shipments would be delayed due to an upgrade of a factory in Belgium, while the EU took a second blow when AstraZeneca said its first-quarter deliveries would be cut by more than half due to production problems.
The EU’s response to that news – which was to threaten tightening export controls on vaccines produced in the bloc – raised another uncomfortable scenario. A world of vaccine nationalism, where there are only enough shots for the most powerful.
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SHORT-TERM HERD IMMUNITY? ‘WHOLLY UNREALISTIC’
While problems with production lines have caught recent headlines, experts say these can be overcome – though probably not in the short-term.
Benjamin Cowling, a professor of epidemiology and biostatistics at the University of Hong Kong’s school of public health, said it was not unusual for manufacturers to overestimate their production rate.
“It is a competitive market and every manufacturer would like to maximise their market share, and underestimating supply could lead to vaccine batches being sold at lower prices,” he said.
Meanwhile Teo Yik Ying, the dean of the National University of Singapore’s Saw Swee Hock School of Public Health, said production delays should not be a long-term problem.
“We should remember that these developers have put in considerable resources to establish and modify their production chains to mass produce Covid-19 vaccines,” he said. The “inevitable” delays, he added, should not be viewed as failures but as “necessary” steps to allow more sustainable and efficient production lines to be established.
Teo said there would eventually be enough doses to cover everyone who wished to be vaccinated, but the real challenge lay in when this could be achieved.
“I anticipate the number of approved vaccines will continue to rise over the next few months, and this means there will be more pharmaceutical production lines coming online to produce doses in large quantities,” he said. “This will allow the world to eventually achieve the number of doses necessary to inoculate the majority of the world’s population.”
However, he said, the time frame would be “longer-term”.
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Lawrence Gostin, a professor at Georgetown University who heads the WHO Collaborating Centre on National and Global Health Law, said it was “wholly unrealistic” to expect the world to achieve herd immunity in the short term.
Low-income countries were unlikely to be able to complete mass vaccination programmes before 2024, he said, owing to costs and vaccine scarcity.
“Even then, the virus is likely to become endemic,” he added.
A recent study by The Economist Intelligence Unit said that among Asian and Pacific economies, only Hong Kong, Singapore and Taiwan were expected to have “widespread” vaccination rates – equating to at least 60 per cent of their populations – by the fourth quarter of this year.
Australia, New Zealand, Japan, and South Korea would accomplish this by the second quarter of 2021, while lower-income nations such as Myanmar and Cambodia – whose GDP per capita is just one fortieth of Singapore’s – might take until 2025 or beyond to reach this goal.
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BIGGER HURDLES AHEAD
Even if distribution problems are a short-term matter, in the longer-term bigger hurdles to herd immunity loom, including logistical problems in transporting vaccines and a general hesitancy among populations to have the vaccines.
Aside from vaccine sceptics, some people are medically ineligible to receive the vaccine while others may be hard to reach because of geographical or socio-economic reasons, said Teo. The WHO currently recommends people with allergies, pregnant and breastfeeding women, and children below 16 should not take the Pfizer-BioNTech vaccine.
Jeremy Rossman, a senior lecturer in virology at the University of Kent, said vaccine costs could end up being “prohibitively expensive”, even for the wealthiest nations and warned that logistical problems in distribution could slow the global vaccination drive.
The International Federation of Pharmaceutical Manufacturers and Associations estimates that a typical vaccine manufacturing plant uses 9,000 materials sourced from 300 suppliers across 30 countries.
Then comes the challenge of distribution. A report by logistics and shipping giant DHL said that delivering 10 billion vaccine doses would require an estimated 15,000 flights, 200,000 movements by pallet shippers, and 15 million deliveries of coolers packed with vials.
This is because some vaccines, including the Pfizer-BioNTech one, need to be stored at extremely low temperatures.
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Given such problems, Rossman said achieving global herd immunity was highly unlikely: “At present, we have nowhere near enough vaccine or logistical capacity to be able to embark on an eradication campaign”.
Teo agreed, saying that even building herd immunity in any single country would be “challenging”, regardless of its wealth.
Finally, there remains lingering fears that new variants of the virus – either those that have emerged in Britain and South Africa or possibly ones yet to be discovered – might be more resistant to the current crop of vaccines or that people’s immunity will fade over time.
Gostin from Georgetown University said this meant that people would need boosters or even new vaccines periodically, which could complicate the global vaccine effort “enormously”.
That, he said, would leave the world facing a “monumental task”.
“I can foresee that rich countries in Asia, Europe and North America will have close to herd immunity by the end of the year, but much of the world will be left far behind,” he said.
“That will have enormous economic, health, and diplomatic consequences.”
