An­ti­body tests could guide eas­ing of so­cial dis­tanc­ing

First pri­or­ity is let­ting health-care work­ers know if they are im­mune

Vancouver Sun - - FRONT PAGE - RANDY SHORE rshore@post­media.com

When re­stric­tions on our per­sonal and work­ing lives are lifted will de­pend on some com­pli­cated math and the level of herd im­mu­nity to COVID-19 that de­vel­ops among Bri­tish Columbians.

Some­where be­tween 30 and 70 per cent could even­tu­ally be in­fected with a novel coro­n­avirus as trans­mis­si­ble as the one that causes COVID -19, ac­cord­ing to Dr. Mel Kra­j­den, med­i­cal direc­tor of the B.C. Cen­tre for Dis­ease Con­trol’s pub­lic health lab­o­ra­tory.

Herd im­mu­nity can slow or halt the spread of a dis­ease when enough peo­ple are im­mune that the novel coro­n­avirus can’t find any­one sus­cep­ti­ble to in­fect.

So, know­ing how many peo­ple have had the dis­ease and are im­mune will be key to de­cid­ing when you can safely get your hair cut or play a pickup game of soc­cer.

The key to know­ing will de­pend on find­ing a re­li­able serol­ogy test, one that can de­tect an im­mune re­sponse to the virus in peo­ple who have had COVID-19 and not known it.

When in­fected with a virus, the body pro­duces pro­teins called an­ti­bod­ies specif­i­cally de­signed to bind to that virus, dis­abling it or mark­ing it for de­struc­tion. Vac­cines are made to stim­u­late pro­duc­tion of those tar­geted an­ti­bod­ies in peo­ple who have never been in­fected.

The pres­ence of an­ti­bod­ies is pre­sumed to mean you are now im­mune to the virus and can­not get it again.

In some pop­u­la­tions, such as those on cruise ships or com­mu­ni­ties in north­ern Italy, from 45 to 75 per cent of peo­ple who tested pos­i­tive for COVID-19 had no symp­toms at the time.

That means many thou­sands of us could have al­ready had the virus and de­vel­oped an ef­fec­tive im­mune re­sponse to it. We just don’t know who or how many.

“We are in the process of val­i­dat­ing whether the ex­ist­ing serol­ogy tests are re­li­able,” said Kra­j­den. “We hope to roll out test­ing for the pur­pose of sup­port­ing front-line health-care work­ers and then un­der­stand­ing the level of im­mu­nity in the pop­u­la­tion.”

Ac­cu­rate serol­ogy test­ing will pro­vide re­as­sur­ance to front-line health-care work­ers, who must deal with the stress of daily con­tact

with pa­tients who have ac­tive in­fec­tions and peo­ple who may be in­fected, he said.

Pro­vin­cial health of­fi­cer Dr. Bonnie Henry is es­pe­cially keen to let health-care work­ers know if they have the an­ti­bod­ies and that they are im­mune.

Know­ing the level of im­mu­nity among all Bri­tish Columbians will be key to de­cid­ing when and if to re­lax the phys­i­cal dis­tanc­ing re­quire­ments needed to slow the spread of the virus, ex­perts say.

“We don’t know how long the im­mu­nity lasts, but we ex­pect it to be at least months,” said Henry.

Test­ing on pri­mates sug­gests that once you clear the in­fec­tion, you are im­mune to the virus, which is the case with closely re­lated coro­n­aviruses.

All the test­ing for COVID-19 to date has been fo­cused on find­ing peo­ple who are ac­tively in­fected with the novel coro­n­avirus to de­ter­mine who can trans­mit the virus to oth­ers.

Serol­ogy test­ing is more like elec­tion polling.

“You don’t have to test ev­ery­body, but you can get some es­ti­mate of who in the pop­u­la­tion has been in­fected and that will help us guide the re­lax­ation of phys­i­cal dis­tance mea­sures,” said Kra­j­den.

Amer­i­can com­men­ta­tors have floated the idea of cre­at­ing a COVID -19 cer­ti­fi­ca­tion sys­tem, or im­mu­nity pass­port, so that peo­ple who are con­firmed to be im­mune can go back to their nor­mal lives and their jobs in or­der to restart the econ­omy as quickly as pos­si­ble.

Kra­j­den was cool to the idea, pre­fer­ring to use such tests to keep the health-care sys­tem func­tion­ing smoothly and to in­form pol­icy mak­ers.

The Pub­lic Health Agency of Canada’s Na­tional Mi­cro­bi­ol­ogy Lab­o­ra­tory is work­ing on de­vel­op­ing a num­ber of sero­logic tests and eval­u­at­ing com­mer­cial sero­logic tests for COVID-19.

“This pan-cana­dian col­lab­o­ra­tion in­cludes mem­bers of the Cana­dian Pub­lic Health Lab­o­ra­tory Net­work, clin­i­cal re­searchers from front-line health-care set­tings, and Cana­dian Blood Ser­vices, all of whom are work­ing to es­tab­lish the ma­te­ri­als needed for both the eval­u­a­tion and then im­ple­men­ta­tion of sero­logic test­ing,” the Pub­lic Health Agency of Canada said.

PETER BATTISTONI

Dr. Mel Kra­j­den of the B.C. Cen­tre for Dis­ease Con­trol says an­ti­body test­ing will help guide the re­lax­ation of so­cial dis­tanc­ing mea­sures.

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