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After months of not knowing how the Covid-19 pandemic would end, we now have some answers. Vaccines that came even faster and work even better than anticipated are the light at the end of this very dark, long tunnel – the beginning of the end is in sight.
But the virus is unlikely to go away for good. The global race to vaccinate as many people as possible will usher in a new phase of our fight against Covid-19, yet there is little chance it will deliver a knockout blow. In the long run, what started as a global pandemic may become yet another example of humankind learning to live alongside a deadly virus.
The end of the pandemic will not happen at the same time for everyone. While countries have welcomed vaccines with open arms – in the UK alone more than six per cent of the population has received at least one dose – other parts of the world are already falling behind in the vaccine race. Despite bearing the brunt of deaths and cases in the pandemic, more developed countries already have a head start on vaccinations.
According to data put together by the Global Health Innovation Centre at Duke University in North Carolina, high-income countries have purchased 4.2 billion doses, compared with low-income countries who have secured just 270 million doses. Some of the world’s richest nations have pre-ordered enough to protect their populations several times over, while some people in low-income countries might have to wait until 2023 or 2024 for vaccination.
In order to achieve herd immunity within a country, it is estimated that around 70 per cent of the population need vaccinations, possibly more. Taking into account the double-dose required by the vaccines currently approved (other vaccines in development, including one from Johnson & Johnson, are single dose), that works out to about 11 billion vaccine doses worldwide.
How long will it be until every country has a vaccination programme up and running? “A long time,” says Toby Peters, a professor at the University of Birmingham. Peters is an expert on cold chains: the logistics involved to move vaccines from the manufacturer to the public while maintaining low temperatures. Vaccines are delicate: they need to be kept at specific temperatures, often away from light – the Pfizer/BioNTech needs storing at -70C in specialised freezers. Any issue in that chain could render the vaccines unusable.
The major issue is that many low- and middle-income countries do not have a reliable electricity supply or infrastructure to keep the vaccines cool. According to the Global Alliance for Vaccines and Immunisation (Gavi), only ten per cent of healthcare facilities in the poorest countries have a reliable electricity supply, while in some countries less than five per cent of health centres have refrigerators suitable for vaccine storage.
Covax, an initiative set up by Gavi, is planning to deliver two billion vaccines to low- and middle-income countries by the end of this year. They have set a target of vaccinating 20 per cent of people in poor countries by the end of 2021, but this is far below what is required for herd immunity. It may be the case that, in a year or two, that most of the developed world has achieved immunity from the virus, but the poorer countries will be left behind.
The solution is “working with countries to put in place the logistics systems to get these vaccines rolled out as fast as possible,” says Peters. Until then, Covid-19 will remain a problem somewhere. “Not only does this me-first approach leave the world’s poorest and most vulnerable people at risk, it’s also self-defeating,” said Tedros Adhanom Ghebreyesus, WHO’s director general, in a recent public address. “Ultimately, these actions will only prolong the Covid-19 pandemic, the restrictions needed to contain it, and human and economic suffering.”
Even if we get a vaccine to everyone in the world, it doesn’t necessarily mean that everyone will be protected for good. That will depend on how the virus reacts, what kind of immunity vaccines will offer, and how long that immunity will last.
Viruses are constantly evolving in order to evade immunity; for example, in the case of influenza, new strains of the virus emerge at such a rapid speed that we need to make new vaccines for every flu season.
Predicting how SARS-CoV-2 will react to the vaccines in the long-term is hard to do, but Danny Altmann, a professor of immunology at Imperial College London thinks it’s unlikely that the virus will evolve into a form that our current vaccines are defenceless against. Sars-CoV-2 seems to mutate at a slower pace than influenza. “It’s quite a sluggish virus,” Altmann says.
It’s possible the virus might not be able to evade the vaccines at all – after all, no strain of the measles virus has ever emerged that can beat the immunity triggered by the measles vaccine. First developed in the early 1960, that vaccine still works just as effectively today.
And though new variants of the virus have begun to pop up around the world, such as the more transmissible B1.1.7 strain first found in the UK, or the newer South Africa variant, or the even newer Brazilian variant, research so far suggests that the new variants do not appear to weaken the efficacy of the vaccines. (Although there is growing concern about one of the mutations found in the South African and Brazilian variants, called E484K, as it appears it may allow them to evade protective antibodies.)
All three of the vaccines currently approved for use in the UK have been developed to target what is called the virus’s spike protein: the part of the virus that allows it to attach to and enter host cells. The vaccines work by inducing neutralising antibodies that bind to different parts of the spike protein. The new variants of the virus don’t appear to change the spike protein enough to mess with the effectiveness of the vaccines. In fact, Pfizer recently announced that its vaccine was found to still be effective against a virus which carried a mutation common to both the UK and South African variants.
Whether the virus evolves to escape the vaccines depends a great deal on whether it is allowed to continue to spread extensively – the longer it circulates, the more it can mutate, and the more dangerous it can become. “I think it would be an error to think of the virus as almost independent of society,” says Deenan Pillay, a professor of virology at University College London.
It’s also not known yet whether the vaccines will be able to stop the transmission of the virus, like the measles vaccine does. “[This] is why we can’t think of vaccines as a single way in which to deal with this,” Pillay says. Stringent public health interventions, such as social distancing, quarantines, border restrictions and so on, slow down the rate at which Sars-CoV-2 mutates, by giving the virus less chances to replicate inside human cells.
Another major unknown is how long the vaccine will protect people for. We might have to get booster shots to maintain immunity every year or every other year, much like the flu shot. Or it may confer longer-term immunity, as vaccination does with measles or polio, due to the fact that those viruses do not mutate nearly as readily as the influenza virus.
It may be the case that in 18 months or more we monitor everybody’s antibody levels, and in the case where levels have fallen in lots of people, we go back and re-evaluate to see if we need to have a vaccination programme the following year that uses a slightly different version of the virus, Altmann says. This is what is done every year with influenza; the vaccine is tweaked ever so slightly to keep up with any new mutations.
“I don’t think immunity will last for a long time, based on what we understand with other coronaviruses,” says Pillay. There are six other human coronaviruses, four of which (HKU1, NL63, OC43 and C229E) are in current circulation and thought to cause a big chunk of all common colds. The remaining two known human coronaviruses, which caused the Sars epidemic in 2009 and Mers (Middle East Respiratory Syndrome) which first emerged in 2012, were both far deadlier, but didn’t have the same ability to spread as widely. Our bodies forget immunity to some of these coronaviruses in about a year, and so it stands to reason that it could be the same for Covid-19. “I think we’ve got to assume that it will be very, very difficult to eliminate this,” Pillay says.
The results of a new study, published in the journal Science on January 12, suggest that once enough people have gained immunity from Covid-19 – either through vaccination or natural infection – that the virus may be “no more virulent than the common cold” in the future; it will, effectively, become the fifth endemic human coronavirus. In the study, the researchers compared Sars-CoV-2 to the other human coronaviruses, and predicted the virus will come to resemble the others in that once you have been exposed to it in childhood, it will cause only mild symptoms or no illness at all in the future – like a cold.
In the case of those who have caught and survived Covid-19, research suggests that immunity to the virus from natural infection could last as long as eight months (although a few cases of reinfection have been reported). However, like for other coronaviruses, it appears that being naturally infected doesn’t seem to induce long-term immunity, so even if someone thinks they’ve had the virus, they still need to be vaccinated, Altmann says – and this is also why the concept of relying on infections to reach the herd immunity threshold remains controversial.
“It seems pretty likely that SARS-CoV-2 will become an endemic coronavirus – that it will become a regular part of the landscape of respiratory viruses that circulate around the world,” says Rosalind Eggo, an infectious disease modeller at the London School of Hygiene and Tropical Medicine. An endemic disease is one that circulates constantly. Other diseases with endemic status include malaria, which continues to spark devastating outbreaks in poorer parts of the world.
Some infectious diseases, such as flu, surge every winter, while others percolate quietly in the background and rear their heads every now and then. Altmann predicts Covid-19 will fall somewhere in between. It could be reduced to seasonal outbreaks like influenzas and other coronaviruses, or it could become uncommon, even rare.
We won’t be rid of it, but we will tolerate Covid-19, to varying degrees; we might enter an age in which, at least until a more robust long-term vaccination programme is put in place, every winter there will be people who will die of Covid-19, with many cases in hospital wards, says Altmann. The world will “accept it as a sort of societal cost”.
Exactly how large, or frequently occurring, that societal cost is will depend on a variety of factors, Eggo says. This includes how long immunity lasts (both infection-acquired and vaccine-acquired), how much transmission is affected by the changing of the seasons, and how – and if – the genetics of the virus changes to escape population immunity. “These big questions will be tackled by scientists over the next months and years,” Eggo says, “and will help us understand, plan for, and mitigate what comes next.”
Spanish flu, which emerged in 1918 and tore across the world, was one of the worst disease outbreaks in history. It infected 500 million people and killed between 50 and 100 million – or five per cent of the world’s population. The outbreak ended only when enough of those who recovered developed immunity. Since then, there have been other influenza pandemics, though none as catastrophic. In 1968, a million people died from the Hong Kong flu; in 2009, a new strain of the H1N1 virus emerged, known as swine flu, which led to a pandemic.
The legacy of these outbreaks remains to this day. Descendants of these strains morphed to become a seasonal flu strain, which comes back, year after year. Sars-CoV-2 could well join them one day.
Grace Browne is a science writer at WIRED. She tweets from @gracefbrowne
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