Ultra-contagious BA.2 Omicron strain adds urgency to second booster injection

The highly contagious BA.2 Omicron subvariant is now the dominant version of the coronavirus in the United States, including on the West Coast – a development that added urgency to federal authorities’ decision on Tuesday to allow a second vaccine booster for people aged 50 and over.

The Los Angeles County Department of Public Health will be ready to offer a second booster to people in this age group starting Wednesday at seven clinics.

An additional injection “is particularly important for people 65 and older, and those 50 and older with underlying health conditions that increase their risk of serious illness from COVID-19, as they are most susceptible. to benefit from an additional booster dose at this stage. time,” Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, said in a statement Tuesday.

Under the new authorisation, a second booster dose will be available for those who are at least four months away from their first booster. This would be the fourth dose for those who were initially vaccinated with the two-dose Pfizer-BioNTech or Moderna vaccines and a third for those who initially received the single-shot Johnson & Johnson vaccine.

Authorities will continue to study the need for a second booster dose for Americans under age 50.

On Tuesday, the CDC also issued a special allowance to all adults who received an initial dose of J&J and a booster of J&J: they are cleared for a second booster, either from Pfizer or Moderna.

The reminders are important because there is evidence of “some decline in protection over time against the severe consequences of COVID-19 in the elderly and immunocompromised,” said Dr. Peter Marks, director of the Center for Food and Drug Administration Biologics Evaluation and Research. declaration.

The CDC has suggested that Pfizer or Moderna vaccines be used for the first or second booster in most situations. A CDC study published Tuesday found that a Pfizer or Moderna booster after an initial injection of J&J was more effective in protecting against hospitalization than a J&J booster.

The CDC has previously recommended that people 12 and older with moderately or severely compromised immune systems who initially received the Pfizer or Moderna vaccine receive a fourth dose, and those with compromised immune systems who initially received the J&J vaccine receive two additional doses.

Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, said in an interview that if he was advising those close to him, he might want people 65 and older — and especially those 75 years and older – receive the second booster. It’s less urgent for a relatively healthy person in their 50s, he said. But a second boost would provide an antibody boost that could help “protect them against breakthrough infection.” An extra dose can also be helpful for people who travel and want to take extra steps to avoid getting infected.

Chin-Hong noted that boosters are safe.

“You don’t get immune depletion; you don’t get more side effects,” he said. “It is well tolerated.”

It will take time for researchers to determine the additional benefit that a second booster will provide. There is a clear benefit after completing the initial vaccination series and again after the first booster, Chin-Hong said. However, early data from Israel suggests that the benefit of a subsequent shot is not as substantial.

“We note a decrease in immunity after the third dose,” said Dr. Robert Kim-Farley, a UCLA epidemiologist and infectious disease expert. “And in some studies, a fourth dose was able to bring the level of antibodies back to what it was shortly after the third dose. This would imply additional protection.

The booster’s expanded availability came the same day the CDC released data estimating that BA.2 — an even more infectious version of the coronavirus than the one that swept through California over the winter — accounts for the majority of new cases. at national scale.

In the week ending Saturday, BA.2 accounted for about 55% of samples nationwide, according to the CDC, up from 39% the previous week. In the Southwest – including California, Arizona, Nevada and Hawaii – BA.2 accounted for about 60.5% of coronavirus samples this week, down from 45%.

There are no signs yet of a sustained increase in new coronavirus cases nationally and in California. In Los Angeles County and statewide, case rates remain at their lowest point since last July, before the Delta surge.

California’s weekly case rate is now 50 per 100,000 people, up from 70 in early March, according to data from Johns Hopkins University.

But about a dozen states are seeing an uptick – including New York, where the weekly case rate fell from 58 per 100,000 people to 105. BA.2 became dominant in the Northeast before doing so on the West Coast.

Some experts say they expect a nationwide increase in cases this spring – a likelihood that could be fueled by the spread of BA.2 and made worse by reduced public masking and increased travel and gatherings.

BA.2 has already fueled substantial increases in other countries, demonstrating how easily the sub-variant can spread.

In Britain, weekly coronavirus cases have more than doubled since late February, and hospitalizations and deaths are rising.

Fueled by BA.2, Britain’s weekly case rate is now around 40% of its winter Omicron peak. According to the BBC, there are reports of hospitals under pressure as healthcare staff have to be sent home due to coronavirus infections.

Many experts believe California is well protected against another large surge because the vast majority of residents have been vaccinated or have some natural immunity to recent infection. But researchers predict California will see an increase in cases.

“We will have a wave. The only question is how big will it be?” tweeted Dr. Eric Topol, director of the Scripps Research Translational Institute in La Jolla.

Added Scripps microbiologist Kristian Andersen: “I expect to see a wave – I don’t know if it will be a surge.”

UCLA’s Kim-Farley doesn’t expect a major surge in the state, “just because so many people are immune, either due to vaccination or natural immunity to recent infection.” He said he would be more concerned about a new variant that would make existing immunizations and natural immunity less effective. He expects the likely scenario for California in the coming weeks to be either a slight increase in coronavirus cases or a steady decrease.

To help LA County avoid a spring surge, it’s very important that unvaccinated people get their shots and eligible people get their booster shots, Kim-Farley said. Only 30% of the county’s 900,000 children aged 5 to 11 are considered fully immunized, and only 62% of its 1.4 million seniors have received a first booster.

Like Kim-Farley, Chin-Hong doesn’t think BA.2 will do much damage in California in the coming weeks, in part due to mild weather allowing people to spend more time outdoors.

At UC San Francisco’s flagship hospital in Parnassus Heights on Monday, there were only four coronavirus-positive patients; none were on a ventilator. In one day at the end of January, there were 95 coronavirus-positive patients, including 12 on ventilators.

There is growing evidence that BA.2 is more contagious than the earlier Omicron subvariant. According to a new study from Sweden – not yet peer-reviewed and published online on Sunday – that analyzed nasal swab samples, the levels of BA.2 virus detected were nearly twice as high as levels of BA.1 .

“A higher viral load in the upper pharynx may at least partially explain why Omicron BA.2 is more infectious than the BA.1 line,” the study states.

Meanwhile, more needs to be done to promote wider public understanding of anti-COVID drugs like Pfizer’s Paxlovid, said Chin-Hong, which is taken orally and can reduce the risk of severe COVID-19 for as long as possible. at 89%.

There have been concerns about recent setbacks involving COVID-19 drugs. First, one of five drugs that treats a novel coronavirus infection, sotrovimab, is likely ineffective against BA.2, and the FDA said Friday the drug is no longer authorized for use in New England, New York and New Jersey.

Second, the failure of Congress to approve new funding for community groups to vaccinate Americans — especially those who are uninsured — could worsen efforts to inoculate people living in vulnerable communities, Chin-Hong said.

In a BBC interview on Sunday, Dr. Anthony Fauci, President Biden’s chief medical adviser, said the United States is heading in the right direction, with hospitalizations and deaths declining. He said he wouldn’t be surprised if eventually an intermittent COVID-19 booster was made available on a regular basis, similar to the flu vaccine.

“We are going, in a gradual way, towards what we all hoped would be normal,” Fauci said. “Having said that, we have to be prepared for the possibility that we have another variant coming forward … which gives us a slight increase in cases and hospitalizations.”

If that happens, he said, “we should be prepared and flexible enough to revert, at least temporarily, to a more rigid type of restriction, like requiring masks indoors.”

Los Angeles Times

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