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COVID tracker: Widespread testing will stay even if we approach ‘herd immunity’

  • NH DHHS—Courtesy

Monitor staff
Published: 3/2/2021 11:44:27 AM

Remember last summer when we were all fixated on the number of COVID-19 tests being run in the state? Not any more!

Now we’re all fixated on the number of vaccine doses being given; testing has been forgotten. Forgotten by us, maybe, but not by health officials.

“Our testing strategy remains the same, and has not changed throughout much of this pandemic,” said Dr. Benjamin Chan, the state epidemiologist. “Until we have a much higher level of vaccination in our populations, we still need to implement these layers of mitigation and protection. Testing is one of those.”

Chan, who spends as much time talking to journalists these days as doing epidemiology (probably to his dismay), recently walked me through our current and future approach to testing.

For the time being, he said, New Hampshire is sticking with the mix of fixed and mobile testing sites, featuring PCR tests for people who don’t have symptoms of COVID-19 and PCR tests or less-accurate antigen tests for people with symptoms.

There’s still community spread of the virus and we need to know how much trouble it’s causing, especially with the arrival of variants that are more contagious and possibly more dangerous.

And what about quick at-home tests, which sure would make life easier?

“This is one of those areas that is in transition,” Chan said. A couple versions of at-home COVID-19 tests have received FDA authorization but require orders from a health-care provider. One called Ellume just got approval for use without such an order.

It’s not clear how accurate these will be in the real world when tissue samples are collected and the test is run by fumble-thumbed people like me, so it’s anyone’s guess how they’ll fit into our overall ability to keep an eye on the spread of the disease. For that reason, they’re not part of the epidemiological mix, at least not yet.

I also asked Chan about what medical folks call the “variants of concern” of COVID-19. Like any virus, SARS-CoV2 has lots of variants but most don’t do anything noticeable, so we’re only concerned about a few of them.

Thus far the state has tested only a few hundred samples for these variants, so we really have no idea which ones are circulating in the state and how widely. Why have we done so few tests?

The complication, Chan said, is that spotting variants requires whole-genome testing, which needs different equipment and protocols.

Basically, a PCR test to determine if someone does or doesn’t have COVID-19 is looking at pre-determined bits of the virus genome to see if something is there, which is pretty straightforward. By contrast, to spot any variants, the test has to look at the whole viral genome (sort of) to see if there are any anomalies, which is much more difficult.

Another complication is that testing for variants is performed only on positive samples, so it has to wait for a first test to be completed, and then collect those positive results for follow-up analysis.

The state has begun to do that. Last month the Department of Health and Human Services sent out its 35th health-provider alert to of the COVID era, asking providers to send specimens to the state lab of any positive cases from people who have recently traveled outside New England (especially if they’ve traveled internationally), or who have gotten vaccinated, or who have previously had COVID-19. If those people get sick, it’s more likely to be caused by a variant.

What all this means is that even if we get to that “much higher level of vaccination” mentioned by Chan, approaching some sort of herd immunity, testing will have to continue to make sure the pandemic doesn’t sneak up on us again. Consider it part of the new normal.

On Friday, Chan talked about vaccines with the Monitor’s Teddy Rosenbluth over Facebook Live. You can see the discussion online.

Meanwhile, the state’s COVID-19 situation is looking pretty good, although the recent outbreaks at big colleges like UNH and Dartmouth is a reminder that things could easily get bad again if we let down our guard.

I’ve added a very quick synopsis of state vaccinations to the list of metrics that the Monitor has been watching since the summer. Daily updated charts and other information can be seen on the Monitor’s COVID-19 page at concordmonitor.com/coronavirus.

How are we doing on vaccinations?

As of last Friday, the state has allocated enough doses of the Moderna or Pfizer vaccines for all 112,000 people in Phase 1-A and about one-third of the 325,000 people in Phase 1-B, which includes everybody over 64. The increasing arrival of doses, especially with the weekend approval of a new vaccine from Johnson & Johnson, makes it likely that vaccinations of Phase 2-A, which includes staff and teachers at K-12 schools and childcare facilities, will start this month.

Number of new cases – what’s the trend? Getting better but still high.

The two-week average of new cases is down to 314, lowest since Nov. 19. But the decline has slowed as outbreaks occur at colleges.

Number of hospitalizations – what’s the trend? Getting better and better.

As of Sunday there were just 87 people in the hospital with COVID-19, also the lowest since Nov. 19. This pattern shows no sign of slowing – the number of hospitalizations has fallen by a third in just two weeks. Very good news.

Number of deaths – what’s the trend? Getting better.

On average, each day in the past two weeks we have seen three deaths from COVID-19. That’s a triple tragedy every day but it is much better than just a month ago.

PCR test positivity rate – what’s the trend? Very good.

This important but obscure number remains below 3%, well below the 5% threshold that raises concern.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)


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