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The Covid-19 virus is evolving rapidly.

That should come as no surprise: RNA-based viruses generate mutations constantly as a result of their error-prone replication. Wherever there are more infections, there are more opportunities for the virus to mutate. For a virus new to a species, as this coronavirus is to humans, some mutations are likely to make it more transmissible.

Important new coronavirus variants have emerged in the United Kingdom, Brazil, and South Africa. What is worrisome about these variants is that even though they evolved independently, they have some similarities. All share the N501Y mutation in the virus’s immunologically key spike protein. The strains in South African and Brazil also share the E484K mutation in the same protein, which some experiments suggest may at least partially evade the antibody response people generate after infection with older strains.


A newly emerging lineage called P.1 with multiple spike protein mutations was identified in 42% of samples tested in December from Manaus, Brazil. The largest city in the Amazon region is being severely hit by the Covid-19 pandemic for a second time: It experienced a similarly fierce first wave in April 2020, leading some to conclude that the population achieved close to herd immunity. That conclusion was wrong, and two possible explanations are that immunity either waned or does not fully protect against P.1.

Alex Hogan/STAT

Multiple scientific groups, including ours, have estimated that the so-called variant of concern in the U.K. (B.1.1.7) is more transmissible than previous coronavirus variants, with estimates varying between 40% and 80%. This likely explains the rapid growth in case numbers seen in Southern England and Ireland over the last two months of 2020. Recently, several groups have reported increased disease severity in people infected with the B.1.1.7 strain compared to those infected with previous strains.


How can policymakers respond to these new challenges? Being aware of them would be a good start. Only a handful of countries, such as the U.K. and Denmark, have large-scale systematic surveillance in place to sequence the genomes of a large enough sample of viruses to track the evolution and rise of new variants in real time. When potentially significant new variants are detected, any changes in transmission, severity, or immunity need to be characterized as quickly as possible.

As countries roll out mass immunization, changes affecting immune recognition will be particularly important to watch for to update vaccine formulation if needed. Fortunately, this pandemic has seen the pioneering of the new technology of mRNA vaccines, such as those produced by Moderna and Pfizer, which should be able to be updated much more easily than older vaccine technologies.

Maintaining control of more-transmissible coronavirus variants is the second challenge. As far as we can judge, B.1.1.7 is no different in how it spreads, it is just better at it in all settings. The same interventions that have been used throughout this pandemic — social distancing, mask wearing, and hand washing — work against the new strains, but their increased transmissibility means that these measures must be implemented more stringently to control the pandemic.

That’s why England went back into lockdown in early January and closed schools. The country is now anxiously studying daily numbers of new cases and hospitalizations to see signs that this third lockdown is working. The early evidence is encouraging: The reproductive number is estimated at between 0.8 and 1.0. Unfortunately, this has not yet translated into hospitalizations, as admissions to critical care have risen to unprecedented levels in many hospitals. The U.K. government is tightening enforcement of existing control measures.

Many countries — at least those high-income countries that have secured adequate supplies of Covid-19 vaccines — are placing their faith in vaccines as a way out of stop-and-start social distancing and lockdowns. The new variants pose additional challenges to this strategy. Even if vaccines are as effective against these new coronavirus variants as they are against older ones, which remains an open question, increased transmissibility means current control measures will need to be relaxed more cautiously than might otherwise have been possible.

And they make achieving high vaccination coverage as rapidly as possible even more critical than before, particularly in the most vulnerable groups. Even vaccinating 80% of individuals over 60 years of age would still leave 20% of the highest-risk age groups unprotected.

Given that the pandemic has so far infected only about 20% of the elderly in the U.S., releasing other control measures and allowing transmission to accelerate in younger age groups would risk causing as many deaths as have been seen so far. It is also unlikely to reduce the pressure on critical care units: Half of patients in U.K. intensive care units are under 61 years of age. Vaccinating older age groups is not going to translate into big reductions in critical care admissions.

Avoiding deaths and critical care admissions will require vaccination strategies to switch their targets from protecting the most clinically vulnerable groups to a strategy that aims at reducing transmission. Such a strategy will generate at least a degree of herd immunity by vaccinating those most likely to transmit the virus: young and middle-aged people, though the effectiveness of this strategy remains to be proven.

What might late 2021 look like? We hope that countries with sufficient vaccine supply will vaccinate a large majority of their adult population, which will prove highly effective, at least at protecting against severe Covid-19.

Yet the U.S., U.K., and other governments worldwide need to prepare for the realistic scenario that some vaccines will only offer partial protection, especially in light of the new virus variants, and that some level of control measures will need to stay in place going into the winter of 2022.

To stay a step ahead of Covid-19, countries need to invest in robust genetic surveillance systems and increase their capabilities to identify coronavirus variants as they arise, and vaccine deployment needs to continue at the same pace or accelerate to safeguard vaccine efficacy as new variants emerge.

The outlook is less optimistic for low- and middle-income countries.

In a globalized world with the risk of virus mutation increased by high levels of infection, no country is protected until all countries are protected. Countries around the globe will need to unite and establish effective governance to combat the global threat from SARS-CoV-2 and its variants.

Neil Ferguson is the director of the Jameel Institute (J-IDEA) and the MRC Centre for Global Infectious Disease Analysis (MRC GIDA) at Imperial College London. Katharina Hauck is the Jameel Institute’s deputy director and lead researcher at MRC GIDA. Christl Donnelly is an associate director of MRC GIDA, professor of applied statistics at the University of Oxford, and a member of the Jameel Institute.

  • I did not notice the authors all have UK email addresses – my comment was intended for people in the US.
    I wanted to add – though it is far from perfect, the Public Health officials in the US, in the absence of adequate actions by the President and CDC, can send officials, state or even county, to airports with international flights, and, depending on state and local laws, require all passengers – because everyone on a flight with one sick person is now suspect – require ALL passengers (and crew of course) to at the least provide contact info, test them on the spot, and require them to allow monitoring so the local officials are certain the Federal rules to quarantine for a week are obeyed.
    The CDC is to blame for not stopping the two variants from entering the US, but even slowing them down, by preventing new cases from flying in, may save a huge numbers of lives if the vaccines actually work against them, or new vaccines which do are rapidly manufactured.

    Please do not be limited by the laws too much – we need to do all we can now.

  • This article said nothing I disagree with, but it’s omissions are important.
    The procedures used to prevent international travelers from bringing the variants here are completely inadequate – the previous administration did not do enough – look at the CDC website to see – we used and honor system – all the way through, actually – the traveler had to show “proof” of a negative test shortly before his flight – there is no indication a forged document would not have worked – the people evaluating the document were to be airline staff – the people at the boarding gate who check your ticket, apparently .

    There is nothing said about retesting on arrival in the US, nor about monitoring the traveler. They say non-US citizens are “required” to quarantine, but it is apparently all honor system – no verification – in Taiwan, they put them under guard – in hotels, not jails, but watched.

    The variants have been known of for months now. And it was known they were, reportedly at least, infecting people who were infected before – in other words, the only thing preventing a brand new epidemic here, the partial herd immunity from previously infected people, would not stop a new epidemic, but STILL the CDC did not take adequate steps to protect us- Trump is to blame as well of course, but if CDC did not have authority to institute true protections and Trump refused to, CDC should have gone public with it. Many travelers likely would have changed their plans even if they just read there was a chance of a long quarantine on arrival.

    As the article said, there is no real hard evidence the vaccines will work against the variants, and even if they do, they are not in many people’s arms yet – additionally, the fact, assuming it is a fact, that the vaccines can be easily modified to make them effective, is not much comfort when we know the “old” vaccines will not be in arms for six more months.

    As this point, it looks very likely we are in for another epidemic – I blame Trump because his travel restrictions were so pathetic, but I blame CDC for not raising the alarm or doing more than they did.

    Dr. Fauci has to stop being everyone’s beloved Family Doctor and be a tough cop instead – in fact, he needed to do that a long time ago. This is a huge failure.

    Even though there is community spread of the South African variant in South Carolina and one case of the Brazil variant in Minneapolis, for now we should still institute real restrictions to keep the numbers down as much as possible. We MIGHT still avoid the Brazil variant and the may be the worst one.

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