Coronavirus Update: 5.04.2020

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IN THE CORONAVIRUS pandemic, rescue from medical advances may not come any time soon—from testing either for infection or for antibodies, or from a vaccine. Alternatively, the human factor creates ongoing uncertainties but also the best hope, which involves concentrating strict social distance regulations in virus hot spots while relaxing them elsewhere for slow, gradual reopening.

Although the pandemic is global, “it is made up of hyperlocal epidemics that are differentially impacting communities,” according to Harvard immunologist Yonatan Grad.

For the four Asian countries—Singapore, Hong Kong, South Korea and Taiwan—that brought Covid-19 numbers down early on and then again following a second wave, two strategies worked: contact tracing and social distancing. Because up to 50% of Covid-19 cases are asymptomatic, nationals returning from abroad managed to pass through various virus checkpoints and to initiate another wave of community infection, which involves unlinked local cases.

In response, the countries imposed 14-day quarantines on every returning national in the “containment” phase, which included “following every infection back through its chain of contacts and isolating all those people from the general population,” according to Wired. Contact tracing can also help pinpoint local “hot spots” of the virus—from cities and towns to medical institutions.

Hong Kong and South Korea “didn’t do so much of physical distancing by shutting down whole cities and regions,” noted David Holtgrave, dean of Albany University’s School of Public Health. Instead, they used testing data and contact tracing to determine where to impose the strictest measures. Likewise, New Zealand has gotten the number of newly diagnosed infections into the single digits and has eased restrictions.

Because containment—testing, identifying and isolating—always misses a few cases, the next phase, “mitigation,” involves social distancing. The goal: to reduce the “reproductive number” (called R0, or r-aught) to below one, meaning that each contagious individual infects only one person or less.

Widespread testing for infection can assess ongoing spread of the virus through a community, as well as determine for individuals when to isolate and begin treating. While infection testing is important for individuals who are regularly exposed to the virus through their work and for those with symptoms, others who are healthy and well protected could get a negative result one day and then have another reason to get tested again the next day.

Testing to detect antibodies—serology tests performed on blood samples—can also give some idea of how much the virus has spread through a community, with the hope that herd immunity will eventually protect individuals. (For individuals, uncertainties of antibody testing, however, remain about what levels constitute protection and how long that protection might last.)

Unfortunately, recent research in New York and California found that for many antibody tests, false positive results—incorrectly indicating the presence of antibodies when in fact the person had no immunity—ranged around 5%.

“Those numbers are just unacceptable,” University of Pennsylvania microbiologist Scott Hensley told the New York Times. False positive results are dangerous both for the individual who incorrectly believes they are safe from infection but also for communities seeking information about how to safely regulate distancing and when to begin reopening.

For antibody testing, another stumbling block is the amount of time following infection before the body produces measurable antibodies as well as for the tests to accurately detect them. Test accuracy, which improves over time, does not approach 80% until at least three weeks following the original infection.

In the New York and California communities, positive results from antibody testing occurred in 2.5 to 15% of the population—with the highest at 24.7% in the epicenter of New York City—far from the 70% minimum needed for sufficient herd immunity to stop, or at least slow, disease transmission.

Another confounding human factor is the variability of the virus, why people get sick from Covid-19 in a wide range of ways: from asymptomatic to severe; from a steady decline to a second wave of illness; from infection remaining in the body for up to six weeks; and from the most severe symptoms occurring in the respiratory system to those in the heart, liver, kidneys, intestines, eyes, nose, brain and toes.

Meanwhile, the currently most-promising drug in development, the anti-viral remdesivir, failed in a Chinese study reported in the Lancet; and even in a recent U.S. study, it shortened hospital stays from 15 to 11 days, but did not reduce the number of deaths at a statistically significant level.  Many older drugs now under consideration for repurposing to treat Covid-19 include Thorazine as well as those used to treat osteoporosis and Parkinson’s Disease.

While research is ongoing for about 90 vaccine candidates, different vaccines may work better for certain groups, like children or older people, or at different dosages, according to Emilio Emini, a director of the vaccine program at the Bill and Melinda Gates Foundation.

Hope soared with the recent announcement that a vaccine candidate at Oxford University could be ready for limited production by the end of the summer. The Oxford researchers had an advantage over other teams, who need to conduct small safety trials before proceeding to the next step, because it had already tried a similar inoculation against an earlier coronavirus.

National Institute of Allergy and Infectious Disease Director Anthony Fauci, however, continues to warn that a widely available vaccine will take at least until Christmas if not longer.

Meanwhile, evaluation of both antibody tests and vaccine candidates could meet a potentially insurmountable obstacle as containment and mitigation become more successful.  As the number of infected people decreases to the point that very little virus remains circulating in a community, it becomes more unlikely that either vaccinated individuals or those with positive antibody results will come into contact with the virus at all —thus making it impossible to collect statistics on efficacy.

In the absence of good treatments or vaccines, contact tracing becomes more valuable. But its reliance on large numbers of people creates another human-factor obstacle, especially in the U.S., where agencies have seen a drop in the numbers of trained staff (those who previously worked on STDs over the past 20 years) from more than 5,000 to around 1,600 today. “The reality is that we at least need a work force of 30,000 people,” according to David Harvey, executive director of the National Coalition of STD Directors; while others place the number at ten times higher.

As of May 1 in the DMV, the  numbers of infections and deaths were still increasing, especially in more disadvantaged areas—numbers that must go down before containment and mitigation can lead to relaxing restrictions and reopening society.

Mary Carpenter

Well-Being Editor Mary Carpenter continues to provide corona virus updates. To read more of her posts, click here.