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Sunday, March 16, 2025

Boosters key to fight omicron, a lot still to learn

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1180 days ago
20211221
City residents wait in a line extending around the block to receive free at-home rapid COVID-19 test kits in Philadelphia, Monday, Dec. 20, 2021. (AP Photo/Matt Rourke)

City residents wait in a line extending around the block to receive free at-home rapid COVID-19 test kits in Philadelphia, Monday, Dec. 20, 2021. (AP Photo/Matt Rourke)

An A.P. EX­PLAIN­ER by
LAU­RAN NEER­GAARD and CAR­LA K. JOHN­SON | AS­SO­CI­AT­ED PRESS

 

(AP) — The new omi­cron vari­ant took on­ly a few weeks to live up to dire pre­dic­tions about how huge­ly con­ta­gious it is but sci­en­tists don’t yet know if it caus­es more se­vere dis­ease even as the world faces ex­plod­ing cas­es just be­fore Christ­mas.

“Every­thing is riski­er now be­cause omi­cron is so much more con­ta­gious,” said Dr. S. Wes­ley Long, who di­rects the test­ing lab at Hous­ton Methodist Hos­pi­tal — and over the past week has can­celled nu­mer­ous plans to avoid ex­po­sure.

Omi­cron now is the dom­i­nant vari­ant in the U.S., fed­er­al health of­fi­cials said Mon­day, ac­count­ing for about three-quar­ters of new in­fec­tions last week.

The speed that it’s out­pac­ing the al­so very con­ta­gious delta vari­ant is as­ton­ish­ing pub­lic health of­fi­cials. In three weeks, omi­cron now makes up 80% of new symp­to­matic cas­es di­ag­nosed by Hous­ton Methodist’s test­ing sites. It took the delta vari­ant three months to reach that lev­el, Long said.

The mu­tant’s abil­i­ty to spread faster and evade im­mu­ni­ty came at a bad time — right as trav­el in­creased and many peo­ple let down their guard. But what the omi­cron wave will mean for the world is still un­clear be­cause so many ques­tions re­main unan­swered.

Here’s the lat­est on what’s known and what’s still to learn about omi­cron.

 

HOW MUCH PRO­TEC­TION DO VAC­CINES OF­FER?

 

Vac­cines in the U.S. and around the world do not of­fer as much pro­tec­tion against omi­cron as they have against pre­vi­ous ver­sions of the coro­n­avirus. How­ev­er, vac­cines still help — a lot. Lab tests show while two dos­es may not be strong enough to pre­vent in­fec­tion, a boost­er shot of ei­ther the Pfiz­er or Mod­er­na vac­cine pro­duces virus-fight­ing an­ti­bod­ies ca­pa­ble of tack­ling omi­cron.

An­ti­body lev­els nat­u­ral­ly drop over time, and a boost­er revved them back up again, by 25 times for Pfiz­er’s ex­tra shot and 37 times for Mod­er­na’s. No one knows ex­act­ly what lev­el is high enough — or how long it will be be­fore an­ti­body lev­els be­gin drop­ping again.

Af­ter a boost­er, the pro­tec­tion against an omi­cron in­fec­tion still ap­pears about 20% less than pro­tec­tion against the delta vari­ant, said Dr. Egon Oz­er of North­west­ern Uni­ver­si­ty.

But if the virus gets past that first line of de­fense, the vac­ci­nat­ed have ad­di­tion­al lay­ers of pro­tec­tion.

“The vac­cines are go­ing to pro­tect you against se­vere dis­ease, hos­pi­tal­iza­tion and death,” said Hous­ton Methodist’s Long. “And that’s re­al­ly the most im­por­tant thing.”

Those ex­tra de­fens­es in­clude T cells that mo­bi­lize to beat back the virus, plus mem­o­ry cells that, once re­ac­ti­vat­ed, race to make more and stronger an­ti­bod­ies.

 

WHAT ABOUT NAT­UR­AL IM­MU­NI­TY?

 

A pri­or in­fec­tion doesn’t seem to of­fer much pro­tec­tion against an omi­cron in­fec­tion al­though, like with vac­ci­na­tion, it may re­duce the chances of se­vere ill­ness.

In South Africa, where omi­cron al­ready has spread wide­ly, sci­en­tists re­port­ed a jump in re­in­fec­tions that they hadn’t seen when two pre­vi­ous mu­tants, in­clud­ing delta, moved through the coun­try.

In Britain, a re­port from the Im­pe­r­i­al Col­lege of Lon­don on Fri­day found the risk of re­in­fec­tion from omi­cron was five times high­er com­pared to the ear­li­er delta vari­ant.

Health ex­perts say any­one who’s sur­vived a bout of COVID-19 still should get vac­ci­nat­ed, be­cause the com­bi­na­tion gen­er­al­ly of­fers stronger pro­tec­tion.

 

WHY ELSE DOES OMI­CRON SPREAD SO FAST?

 

Sci­en­tists are try­ing to de­code the dozens of mu­ta­tions that omi­cron car­ries to fig­ure out what else is go­ing on. Re­searchers in Hong Kong re­cent­ly re­port­ed hints that omi­cron may mul­ti­ply more quick­ly in the air­way than delta did, al­though not as ef­fi­cient­ly deep in the lungs.

What sci­en­tists can’t mea­sure is hu­man be­hav­ior: Many places were re­lax­ing re­stric­tions, win­ter forced gath­er­ings in­doors and trav­el has jumped right as omi­cron be­gan spread­ing.

 

IS OMI­CRON CAUS­ING MILDER ILL­NESS?

 

It’s still too ear­ly to know — es­pe­cial­ly giv­en that if the vac­ci­nat­ed get a break­through in­fec­tion, it should be milder than if omi­cron at­tacks the un­vac­ci­nat­ed.

Ear­ly re­ports from South Africa sug­gest­ed milder ill­ness but doc­tors were un­sure whether that’s be­cause the pop­u­la­tion is fair­ly young — or that many re­tained some pro­tec­tion from a re­cent delta in­fec­tion.

And that British study found no ev­i­dence that omi­cron has been milder than delta in Britain, even with young adults — who would be ex­pect­ed to have milder ill­ness — hav­ing high­er rates of in­fec­tion with omi­cron.

“There’s a hint, and I think many of us are hope­ful, that omi­cron will be less se­vere. But I don’t think we can bet the farm on that. We’re still talk­ing about SARS CoV-2, a virus that has killed mil­lions of peo­ple,” said Dr. Ja­cob Lemieux, who mon­i­tors vari­ants for a re­search col­lab­o­ra­tion led by Har­vard Med­ical School.

 

WHO’S MOST AT RISK?

 

Based on the be­hav­ior of oth­er vari­ants, “if you’re old­er, if you have un­der­ly­ing con­di­tions, if you’re obese, you’re more like­ly to have se­vere dis­ease. I don’t think it’s go­ing to be any dif­fer­ent” than oth­er vari­ants, said Dr. Car­los del Rio of Emory Uni­ver­si­ty.

But even if you don’t get very sick, an omi­cron in­fec­tion could cer­tain­ly ru­in the hol­i­days. Ex­perts agree that in ad­di­tion to get­ting vac­ci­nat­ed and boost­ed, it’s wise to get back to the ba­sics of pro­tec­tion: Wear masks in­doors, avoid crowds and keep your dis­tance.

___

AP Sci­ence Writer Lau­ra Un­gar con­tributed to this re­port.

COVID-19Health


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