Throughout each day, Dr Cheryl Bettigole receives granular, neighbourhood-level updates on the numbers we’ve all been hearing for months – the percentage of people testing positive for Covid-19; transmission rates; hospitalisations; deaths; and progress with vaccines, all in Philadelphia and beyond in the United States.
The lines on the graphs often bounce around like the stock market.
Yet, at some point, the US city’s health commissioner, as well as policymakers throughout the country, have to reduce it all to a pivotal yes-or-no question: Is it okay to resume life as normal?
“Things are trending in the right direction,” Dr Bettigole said last week.
“But we’re not past Covid.”
It is now generally accepted that Covid-19 will always be with us in some form, much like seasonal coronaviruses that cause the common cold.
But thanks to vaccines and the lingering immunity that many have acquired through infection, the share of the population protected from severe disease continues to grow.
That trend has infectious disease experts predicting that sometime in the not-so-distant future – perhaps a matter of months – the disease will become “endemic”, i.e. still circulating, but not out of control.
But what level is low enough to know we’ve crossed that line?
And who decides what is normal?
It’s no secret that plenty of people felt comfortable returning to normal activities months ago (in the US) – eating indoors at restaurants, going to movies, face masks be darned.
Even policymakers such as Dr Bettigole, guided by their public health training to err on the side of caution, have eased up on the toughest, pre-vaccine restrictions.
But with vaccination rates still low in much of the world, the possibility of new SARS-CoV-2 viral variants, and the onset of winter and the flu, they want to make sure that we don’t slide back in the wrong direction.
What ‘endemic’ means
That means an epidemic that has spread across multiple countries, typically affecting large numbers of people.
(In this case, the WHO made the call when 118,000 cases of Covid-19 had been confirmed in more than 100 countries.)
An epidemic, in turn, is a sudden increase in disease “above what is normally expected” in the population of one country or geographic area, the US Centers for Disease Control and Prevention (CDC) says.
Nothing about Covid-19 was normal. It was brand-new, after all.
Endemic, on the other hand, means that a disease has reached a “constant” or “usual” presence, the US federal health agency says – in other words, normal.
Yet, even after all this time, Dr Bettigole says it is hard to tell what level of Covid-19 will constitute its endemic phase.
In the near future, the threat level may continue to wax and wane as it has throughout the pandemic, she says.
And the disease may subside enough in one region for a health department to lift face mask requirements and other restrictions, but not in others, she predicts.
In her office at the Philadelphia Department of Public Health, she keeps a close eye on surrounding counties, noting that the city, while less vaccinated than its neighbours, currently has lower rates of Covid-19 – a trend she attributes to Philly’s continued face mask requirement.
“I think this could be a little like forest fires,” she says.
“I think it would be possible to say at a future time when the numbers look good, ‘Hey, we don’t need to have masks right now, (but) we might in the future.’”
How low is low enough?
We all remember the start of the pandemic, when naysayers described Covid-19 as “just like the flu”, despite clear evidence that its impact was far more severe.
Even this year (2021), despite the advent of effective vaccines, close to 400,000 deaths in the US have been attributed to Covid-19 – 10 times the typical national death toll each year from the flu.
But if Covid-19 deaths and hospitalisations did eventually reach levels usually associated with the flu, would that be a reasonable benchmark for saying the pandemic was over?
It’s not that simple, says Dr Donald F. Schwarz, a former Philadelphia health commissioner who is now a senior vice-president at the Robert Wood Johnson Foundation.
With the flu, nearly everyone has some level of baseline immunity, he says.
The world is not there yet with Covid-19.
And unlike Covid-19, the flu is seasonal, meaning that health officials in the northern hemisphere have time to prepare each year based on what flu strains are circulating below the equator, he says.
Not so with Covid-19.
“If there’s any (Covid-19) outbreak in Brazil in the summer, we’re all at risk in a way that we would not be with influenza,” he says.
“A new variant of Covid-19 in any part of the world is a risk to all of us.”
In Philadelphia at the moment, 2% of those getting tested for Covid-19 are identified as positive – well below the 5% threshold that epidemiologists say is cause for heightened concern.
Dr Bettigole says she would like the city to do even better, reaching a positivity rate below 1%.
But as more people are vaccinated – meaning that fewer people are likely to become infected and suffer life-threatening symptoms – case counts and positivity rates alone may be less important, she says.
“If our case rate is high and no one’s in the hospital, or very few people are in the hospital...” she says, “if people aren’t ending up in the hospital or aren’t ending up dying with complications, that might be something we can live with.”
Potential ‘twindemic’
The US was largely spared from the flu last winter (2020), a phenomenon generally attributed to all the physical distancing and other restrictions that were in place due to Covid-19.
But some infectious disease experts have warned the flu may come back hard this winter (2021) while Covid-19 remains widespread – a so-called “twindemic”.
For those getting a Covid-19 booster, a flu shot is recommended on the same visit.
Dr Herb Conaway, director of the Burlington County Health Department and a New Jersey state assemblyman, is among those cautioning that it is too soon for society to let down its guard.
“We’re moving to winter,” he says.
“That means less outdoor activities, more people huddled together in drier air indoors (and) more likely to engage in what might be considered high-risk behaviour.”
If there is a silver lining in the post-pandemic future, he says, more people may choose to be vigilant about hand-washing and other precautions – even wearing face masks when not required.
“I think there will be a number of people who will continue to wear masks even when we reach this endemic phase,” the physician says.
“They might wear it on the train or on a bus or on a plane, might wear it in other venues where they’re huddled close together.”
What about new mutations?
Each month seems to bring a new coronavirus variant somewhere in the world, even as Delta retains a strong foothold globally.
The good news is that none of the viral variants has mutated enough to escape the protection that vaccines provide against severe disease, says Dr E. John Wherry, an immunologist at the University of Pennsylvania’s Perelman School of Medicine.
Yes, there have been breakthrough infections in vaccinated people.
But that’s not because our antibodies and other defences fail to “recognise” Delta, says the university’s Institute for Immunology director.
It’s because our antibody levels have declined.
And in the case of Delta, because its mutations have made the variant more transmissible.
That attribute allows the virus to start making copies inside the host – the definition of infection – before the immune system has time to snuff it out.
Still, the cells that produce antibodies, called B-cells, retain the blueprint for making more of them in a hurry, meaning that most infections in vaccinated people will not escalate to a severe case of Covid-19.
“The risk of a really, really concerning variant arising is not super high,” he says. “But it’s not zero either.”
That’s because the vaccines train the immune system to recognise the coronavirus “spike” – the tool that it uses to enter human cells.
So, if the spike mutates enough that the immune system has trouble recognising it, those mutations can also be self-defeating: making the spike less adept at penetrating cells.
The danger would be if the virus evolved two “compensatory mutations” at the same time – one enabling it to escape the immune response and the other restoring its infectivity through some other means, Dr Wherry says.
But that’s unlikely. “You need two independent things to happen at the same time,” he explains.
“But the longer the virus replicates, the more you’re rolling the dice.”
Vaccine coverage needed
Public health experts say the road to normal, however that is defined, involves – no surprise – vaccines.
In the US, boosters have been recommended for people in various age groups – in some cases, depending on underlying medical conditions or on which vaccine they initially received.
The shots should generally boost the level of antibodies circulating in the person’s bloodstream, potentially preventing even mild infections, Dr Wherry says.
Far more effective, however, would be to vaccinate people who have yet to receive any shots, according to a new review of the evidence from ECRI, a Plymouth Meeting-based nonprofit that evaluates the safety and quality of healthcare.
“The focus should remain on vaccinating as many people as possible,” says Marcus Schabacker, the research institute’s president and chief executive officer.
Progress is steady in the US, though uneven, and the numbers should rise even more as the Pfizer/BioNTech vaccine has recently been authorised for children ages five to 11.
But success remains elusive in much of the rest of the world.
As of Sept 23 (2021), just 2.1% of residents in low-income countries had a single dose of a vaccine, the ECRI report found.
The figure had climbed substantially as of Nov 1, hitting 3.6%, but remains well behind the numbers in developed nations.
That disparity is foremost a humanitarian issue, the report’s authors wrote.
And as many have noted, it also paves the way for new viral variants abroad that could travel to the US – more rolls of the dice. – By Tom Avril, Jason Laughlin and Laura McCrystal/The Philadelphia Inquirer/Tribune News Service
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