COVID-19 VARIANTS MAY UPEND RECOVERY HOPES
The provincial health officer warned Friday that new and more transmissible variations of COVID-19 could be “a spanner in the works” for the plan to achieve herd immunity in B.C.
“Herd immunity, or what I call community immunity … is what we are aiming for in British Columbia,” Dr. Bonnie Henry reminded reporters during a briefing Friday. “Community immunity means that the virus can't find ways to transmit to lots of people in our community. And getting there will mean a large number of our population need to be protected.”
She made the comments at the rollout of an ambitious plan to dispense two doses of vaccine to every British Columbian aged 18 and over by the end of October.
Presuming the province comes close to that target, it would be well within the preliminary estimate for herd or community immunity, the successful vaccination of 60 to 70 per cent of the population of B.C.
The calculation is based on the reproduction rate of the virus — how many additional people are infected by each carrier. But lately the initial estimate has been cast into doubt by the discovery of variants of the virus that are more infectious.
Henry addressed those concerns Friday when asked when British Columbians would be able to shed their masks and return to more normal life.
“I would love to be able to say July 1,” she replied, “but there are a whole lot of unknowns.”
Not least whether the federal government can deliver promised supplies on schedule and whether the province is able to avoid a repeat of this fall's second-wave surge.
“The one spanner in the works is the fact that we're now seeing transmission of variants across the world,” she cautioned. “Some of these make the virus more transmissible to others. ”
She mentioned U.K. and South African variants, both of which have shown up in B.C. courtesy of travellers from overseas.
The U.K. variant has already given rise to concerns that it may be necessary to vaccinate more than 80 per cent of the population to achieve herd immunity.
Dr. Anthony Fauci, the U.S. expert on infectious disease, has been saying for weeks that the 60-70 per cent estimate is “undoubtedly” too low.
“We need to have some humility here,” he told Donald Mcneil of the New York Times last month. “We really don't know what the real number is. I think the real range is somewhere between 70 to 90 per cent. But I'm not going to say 90 per cent.”
The higher number would be just a few percentage points below the herd immunity threshold for measles, considered the world's most contagious disease.
“I'll bet my house that COVID isn't as contagious as measles,” said Fauci.
When Henry was asked recently about Fauci's estimate, she turned it into a teachable moment about the relationship between herd immunity and reproduction rates.
“What I think Dr. Fauci and others are concerned about is the increased transmissibility we're seeing with the U.K. variant,” she said.
“As the R-nought (R0 or reproduction rate) goes up, then you need to have more people protected before you can prevent those transmissions so the virus runs into dead ends.
“If we look at an R0 around two-ish, if 60 to 70 per cent of the population is immunized, that should prevent those transmissions to most people.”
She acknowledged that preliminary estimates for the U.K. variant suggest it would boost the reproduction rate to three, which would mean a corresponding increase in the vaccination percentage necessary for herd immunity.
But in Friday's briefing, she also emphasized other factors that could make the pandemic more manageable, including federal approval of additional vaccines and a decline in infectiousness with the arrival of spring and summer weather.
“I am hopeful that by the summer we should be able to have some types of our normal lives back again,” said the provincial health officer. “But the full (return) to what we would like to have in terms of social interactions and being together is not likely until the fall.”
Optimism aside, a higher threshold for herd immunity could have implications for travel, workplaces, public safety and other pandemic-related restrictions.
If only, say, 70 per cent of the population needs to be vaccinated to dead end the spread of the virus, then a 30 per cent refusal rate on the vaccine could be tolerated.
But if all but 10 per cent of the population needed the vaccination to reach herd immunity, there would be corresponding pressure to make vaccinations mandatory in some settings.
The prospect came up Friday when the government announced that it intends to issue “proof of vaccine” certificates and “immunization cards” for those who've received the necessary first and second dose.
The certificates and cards sounded a bit like the “vaccination passports” that are being proposed in other jurisdictions for air travel and to entering some stores, restaurants and workplaces.
The government handout says the vaccination records “will be stored in the provincial immunization registry accessible by public health, their own physician and themselves.”
They cannot be used against the unvaccinated to deny access to provincial services.
Still, if herd immunity proves to be as difficult to achieve as it might be, I would not be surprised to see demands for people to produce their proof of vaccination in some situations.
The U.K. variant has already given rise to concerns that it may be necessary to vaccinate more than 80 per cent of the population to achieve herd immunity.