It has only been around a little more than a month, but the Omicron variant of the SARS-CoV-2 virus that causes Covid-19 has taken over. It was first detected in Botswana and South Africa in mid-November and was reported to the World Health Organization on November 24. Two days later, WHO named it a variant of concern, a designation that the U.S. confirmed two days after. On December 1, the first confirmed U.S. Omicron case was identified. Now, just three weeks later, Omicron accounts for three-quarters of new U.S. Covid-19 cases and over 90 percent of cases in the New York metropolitan area.
Omicron has led to a surge in new cases, including many breakthrough cases in the vaccinated. The good news is that, while vaccines may be less effective in defeating Omicron transmission than with earlier variants, the vaccines appear to retain their effectiveness in preventing severe disease. But even though a smaller proportion of Omicron cases goes on to severe illness, a large enough increase in infections would create the possibility of increased hospitalizations and deaths. And with increasing infections, hospitalizations, and deaths, public-health officials may return to the destructive lockdown mentality.
Cheap, rapid, readily available at-home tests could short circuit this possibility by helping to control the outbreak. They would give people the option to reassure themselves that they are not ill or endangering others without having to wait for tests that only yield results days later. Unfortunately, rapid at-home tests are still scarce, and scenes of anxious people lining up around the block for tests at medical facilities are common around the country.
President Biden has tried to excuse the testing shortage by claiming that no one could have anticipated the rapid arrival of a new, highly transmissible variant and the need for easily available testing. His explanation strains credulity. The highly transmissible Delta variant has been surging around the country for months. The possibility that new, even more transmissible variants could arise was well known. That is why Biden’s new announcement that the federal government would purchase and distribute 500 million rapid, at-home tests to Americans is too little, too late.
As my colleague Mario Loyola and I wrote back in March 2020, making “cheap, rapid testing available to every individual” was key to fighting the pandemic. Since Covid-19 often caused mild or no symptoms, widespread testing was the only way individuals could ascertain their status and their need to isolate so that they did not infect others. It was also needed to provide public health authorities with more accurate information on where disease outbreaks were occurring and the real number of infections, so that the true infection fatality rate could be calculated.
Due partly to early miscues by the FDA and CDC, tests were in short supply early in the pandemic. Moreover, the early tests were all reverse-transcriptase polymerase chain reaction (PCR) tests, which medical personnel had to administer and laboratories took days to process. We suggested that developing antigen-based tests that could be self-administered at home and give results in minutes rather than days was essential and urged the FDA to relax its guidelines to approve such tests as soon as possible.
As Rochelle Walensky—then head of infectious disease at the Massachusetts General Hospital and now CDC director—pointed out in September 2020, rapid antigen-based tests are better for outbreak control than the gold standard PCR tests. The PCR tests for bits of viral matter that can persist for weeks, well after the five-to-seven days a patient is infectious to those around them. Thus, PCR tests are highly sensitive (meaning that they rarely give a false negative) for diagnosing infection but can yield a positive result long after a person ceases to pose a risk of transmission to others.
Infectiousness depends on viral burden or load: the number of viruses you have in your airways. The antigen test looks for proteins in those viruses. If the viral burden is low because it is very early in the infection—or low because it is later, when the number of viruses has peaked and started to decline—then the patient is less infectious to others. If the viral burden is high, making the patient more infectious, there is a greater likelihood of the test showing a positive antigen result.
The upshot is that, while the antigen test is less sensitive for diagnosing infection (more likely to give a false negative), it is more specific (less likely to give a false positive) for diagnosing infectiousness. Since cheap, at-home tests make it easier to test repeatedly, there is less likelihood that a false negative would slip through. Walensky concluded, “Rapid, saliva-based antigen testing is an essential weapon in the fight to resume many of the activities and reopen many of the venues that comprise what we used to call ‘normal life.’ It is practical, convenient, cost-effective, and easily scaled. . . . it is time to start asking why it is taking the FDA so long to approve this essential prevention technology.”
That is still a good question. Unrealistic FDA approval standards and bureaucratic foot-dragging limited approval of rapid at-home tests here, so that the tests are far more expensive and hard to find than they are in Europe. Companies large and small have complained about FDA inflexibility. Europe has about four times as many over-the-counter, at-home tests available as does the U.S.
The Biden administration could have followed the Operation Warp speed vaccine approach by making large test purchases from manufacturers. This would have encouraged more makers to pursue authorization and ensured a supply that could be distributed at low or no cost to consumers. But the administration rejected that approach.
The newly announced plan to purchase and distribute 500 million rapid tests will not have an impact until late January and assumes test makers can rapidly ramp up production and distribution. The rapid rise and decline of Omicron cases in South Africa suggests that, even if everything goes perfectly, we may be past the peak of an Omicron wave before at-home tests are widely available.
People are willing and anxious to be tested. This is likely true even for the millions of people who refuse vaccination and especially for their families who do not want to put them at risk. Providing cheap, readily available testing can interrupt the spread of Omicron and future variants. It’s a shame that government officials didn’t recognize this earlier.
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