That winter surge of COVID-19? It seems to be happening, although recall rates remain low

As an expected winter surge arrives, less than one in five San Diego County residents who qualify for a bivalent coronavirus booster shot have had one, according to local vaccination reports.

The recall rate is becoming increasingly relevant as local sewage shows a steady increase in the amount of virus circulating in the community since Halloween and emergency services are already dealing with an early flu season.

Dr. Robert “Chip” Schooley, an infectious disease expert at UC San Diego Health, said enough time has now passed with gradually increasing numbers to suggest the predicted winter surge is coming.

“We kind of hit rock bottom on Halloween with about 740,000 copies of COVID in the sewage samples, but we’re at about four times that amount now,” Schooley said. “When you have a fourfold difference, that’s not noise…we’ve clearly been in an uptrend since late October.”

The number of local COVID-19 cases detected through testing and the number of coronavirus-related hospitalizations are also increasing, although so far these trends have not come close to the peaks seen during the summer months, and still less last winter.

The SEARCH coalition of local San Diego research labs has also returned to regular public updates that indicate which coronavirus subvariants have been making the rounds recently. As expected, BQ.1 and BQ.1.1 – versions that have already caused surges in Europe and elsewhere in the world – are now spreading locally.

Nationally, the US Centers for Disease Control and Prevention says BQs, which have key mutations that help them evade immune system protections, now account for about half of all new cases.

The most recent analysis from San Diego from Nov. 9 estimates that about 22% of cases were caused by BQ.1.1 while BQ.1 was only responsible for about 4%.

The shift from the variants that caused this summer’s surge to a new crop comes as protection from previous infections wanes. Those two factors working together, Schooley said, should lead to higher infection rates as winter arrives.

“I think we are going to see a good number of cases over the winter season which will hopefully lead to less morbidity and mortality and hopefully more nuisance cases which may cause people to off work,” Schooley said.

But less serious cases may come down to vaccination, with studies showing that even when infection is not prevented, the chances of ending up in a hospital bed are significantly reduced.

Many who had a relatively mild case of COVID-19 over the summer may think their immune systems are sufficiently well prepared for whatever is coming this winter that a booster shot really isn’t necessary.

But previous spurts of this three-year-old coronavirus slog have taught researchers that protection, whether achieved by fighting an infection or through a vaccine, doesn’t last forever.

Shane Crotty, a vaccine researcher and virologist at the La Jolla Institute for Immunology, felt that six months is a good interval for a new boost for the immune system to produce a new batch of antibodies and other protective components. Others say the protection begins to wane about three months after a previous encounter.

“If getting a five-month booster makes you more comfortable, that’s fine, too,” Crotty said.

While young people have tended to go through several coronavirus flare-ups with mild illness, that’s not the case for those with pre-existing conditions, and especially those who are older.

For the roughly 2 million people in San Diego County who are currently unstimulated, Schooley said it now makes sense with the holiday season on the horizon. Those who have already been vaccinated or infected, he said, have the added benefit of seeing a faster response than was the case for the first vaccines in 2021.

“When your immune system hasn’t seen anything before, it can take a week or two to see a response,” Schooley said. “But when you have a memory response from a previous encounter, you start to build more immunity within just a few days.

“You don’t hit your peak immunity right away, but you start to see things coming out of the immune system much faster when you’ve already had a priming experience.”

Kristian Andersen, a virologist at Scripps Research, agreed, adding that the timing of the reminders was right.

“Of course, don’t do it right after you got COVID, but if it’s been several months and it’s been (at least) six months since your last shot, go get your shot every two years,” Andersen said in an email.

The current dual-purpose booster targets parts of the BA.4 and BA.5 sub-variants that spread across the world mid-year. But makers have found the product generates antibodies against a wide range of coronavirus types, including the BQ versions which are now spreading the fastest.