The World Health Organization declared Covid-19 a pandemic on March 11 one year ago. The question now is when will it be over?
Experts say an end to the pandemic will be less defined than its start, as different countries subdue the disease at different times. But they agree that while vaccines were developed in record time, the virus is here to stay.
“We’re not headed for a Covid-free future,” said Jodie McVernon, director of epidemiology at the Peter Doherty Institute for Infection and Immunity in Melbourne. “Really, what we are aspiring vaccines to do for us is hasten the transition [away] from this being a catastrophic, overwhelming epidemic disease with high death rates,” she said.
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Some medical experts say the Sars-CoV-2 virus may become a seasonal infection like the flu, while others say it’s more likely it will just circulate at low levels for years, with the potential for resurgences, which could be complicated by new strains of the virus.
WHO chief Tedros Adhanom Ghebreyesus made the pandemic call on the disease 12 months ago when 118,000 people had been reported infected in 114 countries. He said: “All countries can still change the course of this pandemic”.
Governments chose different methods to protect their populations, and yet the disease has caused more than 2.6 million deaths, the infection of 117 million people and has driven the global economy into the biggest slump in nearly a century.
Now the roll-out of vaccines brings hope that countries can do this year what Tedros called on them to do last: change the course of the pandemic.
“An end to the pandemic would be an end to the threat of a surge in infections and illnesses that could overwhelm a health care system,” said Ben Cowling, a professor of epidemiology at the University of Hong Kong’s School of Public Health.
For example, the United States and Europe, though a combination of mass vaccination and immunity gained through infection, may see a “return to normal” with some minimal disease control measures in the next few months, he said.
This might take longer in Asia, he said, where low infection rates in some places meant populations must rely on a wide vaccine roll-out to reach herd immunity. Coronavirus herd immunity is generally thought to occur when at least two-thirds of a population are immune to the virus that causes Covid-19.
At that point, “the virus will continue to circulate for many years to come, but it will not pose a major threat to health care systems”, Cowling said.
Experts do not yet know what that circulation will look like. One theory is that in temperate climates the virus could have seasonal upticks like the flu, affecting pockets of the population who are not immune.
A commonly held view is that rather than being seasonal, the virus will continue to circulate at low levels, with the potential for resurgences among vulnerable populations or if immunity wanes.
The wild card
But just as vaccines roll out, virus variants have raised concerns. Mutations that happen naturally as the virus spreads could give rise to strains that slip past human immune defences and interfere with herd immunity.
“One could think that the variants emerge in such a way that they are new viruses,” said Jon Andrus, an adjunct professor of global health at George Washington University’s Milken Institute School of Public Health. “So the hope that we have for achieving immunity against the original virus goes out the window. That’s one scenario.”
Preliminary evidence relating to a variant first identified in South Africa and another in Brazil suggests that people previously infected by the older strains could be at risk of a second infection with these new ones.
Similarly, clinical trial results have shown certain vaccines have reduced efficacy against variants.
But more information is needed to understand the implications of both sets of findings, such as whether people are still protected against severe disease, even if they can become ill.
Andrus said vaccines might be modified every year to try to stay up with the evolution of variants, as is done with seasonal influenza. “Perhaps we’ll need a yearly boost,” he said, noting it was too soon to know.
A number of vaccine developers are working on vaccine updates to be ready if needed, and work is under way to figure out how best to monitor these strains globally – a process already done with influenza.
Immunologist Ashley St. John, an associate professor at Duke-NUS Medical School in Singapore, said evidence showed current vaccines were still critical tools to protect against the virus, and any decrease in efficacy might simply mean more people vaccinated needed to reach the same level of efficacy in a community.
“The real challenge is getting everyone up to the stage of herd immunity, and then if we start seeing in a few years that there are breakthrough cases from new strains, we can tweak the vaccines the same way the flu vaccine is tweaked,” she said.
The timeline for getting the pandemic under control – and seeing a gradual return to normalcy – would depend on how quickly people around the world were vaccinated, according to St. John.
“As we do start having more vaccinated individuals, we can move to a system where we are trusting the vaccine to keep people safe,” she said, noting this would build over time as populations reached the herd immunity threshold needed to prevent spread.
The access gap
WHO’s goal is to end the “acute phase” of the pandemic, reducing hospital admissions, deaths and severe illness around the world by the end of this year.
Their plan hinges on the success of a global vaccine distribution mechanism known as Covax Facility, meant to address a failure of past health crises where rich nations had vaccines or treatments long before poorer ones.
By next Monday, 34 million of the 2 billion doses expected to be distributed through Covax Facility this year will have been delivered, according to WHO.
But those 34 million doses, split between 51 countries, pale next to the number of doses used so far in the United States and China, two vaccine-producing countries. The overall aim for Covax Facility is to reach 20 per cent of populations in participating countries before the year’s end – far below that needed for herd immunity.
During an interview on CNBC on Monday, philanthropist Melinda Gates said global herd immunity could be reached “some time in 2022”. Gates is co-chair of the Bill and Melinda Gates Foundation, a major backer of the institutions running Covax Facility.
The urgency is clear, medical experts say, because the more the virus is allowed to spread, the more potential there is for new strains to emerge and circulate as people meet and travel.
“The more we can collectively take action, and think of it as a global problem that requires a global solution … the more likely we’ll have success,” said Andrus in Washington.
“It’s a race … and that race has to be won everywhere.”
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This article Coronavirus: the pandemic is now one year old, so when will it be over? first appeared on South China Morning Post