Since the emer­gence of the Omi­cron vari­ant of the coro­n­avirus, cas­es of COVID re­in­fec­tions are be­com­ing more com­mon.

By Eliz­a­beth Me­limopou­los-Al­jazeera

As the Omi­cron vari­ant of the coro­n­avirus dri­ves new waves of COVID in­fec­tions around the world, some ear­ly stud­ies ap­pear to show the risk of re­in­fec­tion has risen.

Ac­cord­ing to an analy­sis by the Unit­ed King­dom’s Of­fice for Na­tion­al Sta­tis­tics (ONS), the risk of re­in­fec­tion is 16 times high­er when Omi­cron was the dom­i­nant vari­ant, com­pared with the pe­ri­od when Delta was dom­i­nant.

The analy­sis al­so showed that un­vac­ci­nat­ed peo­ple were twice as like­ly to be re­in­fect­ed than those who had their sec­ond dose of vac­cine in the pre­vi­ous 14 to 89 days.

With in­fec­tion rates con­tin­u­ing to surge across most re­gions around the world and as the num­ber of re­in­fec­tions al­so climbs, ex­perts have said that pro­tec­tion from pre­vi­ous in­fec­tions or vac­cines de­clines over time.

What is a re­in­fec­tion?

A re­in­fec­tion is a med­ical con­di­tion that usu­al­ly oc­curs when a per­son be­comes in­fect­ed with COVID-19, re­cov­ers, and then gets in­fect­ed again. It could hap­pen with any of the vari­ants of the coro­n­avirus.

Ac­cord­ing to the Unit­ed States Cen­ters for Dis­ease Con­trol and Pre­ven­tion (CDC), a re­in­fec­tion is con­sid­ered such if the pa­tient “tests pos­i­tive again 90 days or more af­ter their first pos­i­tive test”. The same stan­dard has been es­tab­lished by the UK Health Se­cu­ri­ty Agency (UKHSA).

The 90-day pe­ri­od has been cho­sen be­cause some pa­tients con­tin­ue to have the virus in their sys­tems for longer than the av­er­age of about two weeks, mak­ing it dif­fi­cult to dis­tin­guish be­tween an in­fec­tion or a re­in­fec­tion with­in this time frame.

“The ma­jor­i­ty of pa­tients with nor­mal im­mu­ni­ty do not have the virus be­yond 10-14 days, but some har­bour it for a longer time and there­fore the time has been ex­tend­ed to three months,” Dr Pere Domin­go, cur­rent­ly se­nior con­sul­tant and HIV/AIDS pro­gramme di­rec­tor at the In­fec­tious Dis­eases Unit of the Hos­pi­tal de la San­ta Creu i Sant Pau, told Al Jazeera.

Is this risk of COVID re­in­fec­tion ris­ing?

Ac­cord­ing to a re­port pub­lished by the UK’s ONS in June 2021, re­in­fec­tions were con­sid­ered rare, but the rate of re­in­fec­tions has in­creased since the Omi­cron vari­ant be­came the dom­i­nant strain in late 2021.

An analy­sis pub­lished last week by the news agency Reuters, cit­ing da­ta col­lect­ed by the UKHSA, sug­gest­ed that sus­pect­ed re­in­fec­tions ac­count­ed for ap­prox­i­mate­ly 10 per­cent of con­firmed cas­es in Eng­land in Jan­u­ary. Sus­pect­ed re­in­fec­tions made up few­er than 2 per­cent of cas­es in the six months pri­or to De­cem­ber 6. A to­tal of 588,000 pos­si­ble re­in­fec­tions have been reg­is­tered in Eng­land.

Mean­while in Italy, 3 per­cent of the new cas­es were re­in­fec­tions, up from about 1.5 per­cent be­fore Omi­cron, a spokesper­son for Italy’s Na­tion­al In­sti­tute of Health said last week.

Dr Domin­go not­ed that the Omi­cron vari­ant has mu­tat­ed sig­nif­i­cant­ly com­pared with oth­er vari­ants, mean­ing that pro­tec­tion de­vel­oped against pre­vi­ous vari­ants could be less ef­fec­tive against Omi­cron.

“Omi­cron has mu­tat­ed many times,” Dr Domin­go said. “These mu­ta­tions have changed the anti­gens, the pro­teins are no longer the same as they were in Delta, nor the strain that came out in Wuhan.

“There­fore, the an­ti­bod­ies that one could de­vel­op against the orig­i­nal strain or against Delta, are no longer use­ful for Omi­cron,” he added.

Ac­cord­ing to the re­search by Im­pe­r­i­al Col­lege Lon­don, the pro­tec­tion af­ford­ed by the past in­fec­tion may be “as low as 19 per­cent”.

Why are cas­es of re­in­fec­tions ris­ing?

Virus­es are con­stant­ly evolv­ing and these changes nat­u­ral­ly lead to the emer­gence of new strains that can lead to new in­fec­tions.

“There is al­ways a strug­gle be­tween the forces of the in­di­vid­ual and im­mu­ni­ty on the one hand and the virus on the oth­er,” Dr Domin­go said.

“And the way the virus fights is by chang­ing, by mak­ing mu­ta­tions that will al­low it to avoid the pa­tient’s an­ti­bod­ies,” he added.

Ac­cord­ing to re­search from South Africa, peo­ple in­fect­ed with Omi­cron de­vel­oped an an­ti­body re­sponse to the cur­rent and pre­vi­ous strains. How­ev­er, ac­cord­ing to the Gavi vac­cine al­liance, the im­mu­ni­ty from a Delta in­fec­tion pro­vides lim­it­ed pro­tec­tion against Omi­cron.

Pre­vi­ous in­fec­tions or vac­cines will pro­vide pro­tec­tion, and the greater the ex­po­sure to the virus leads to greater pro­tec­tion, but the “im­mu­ni­ty is not com­plete and it de­clines over time,” Dr Domin­go said.

“And if the virus changes, the pro­tec­tion gen­er­at­ed by in­fec­tion, is over­whelmed.”

Are re­in­fec­tions less se­vere?

Ac­cord­ing to ear­ly re­search, re­in­fec­tions are gen­er­al­ly mild. A study done in the state of Qatar found that re­in­fec­tions “have 90 per­cent low­er odds of re­sult­ing in hos­pi­tal­i­sa­tion or death than pri­ma­ry in­fec­tions”.

Dr William Schaffn­er, pro­fes­sor of med­i­cine at Van­der­bilt Uni­ver­si­ty Med­ical Cen­ter, said the sever­i­ty of a re­in­fe­tion de­pends on the pa­tient’s im­mune sys­tem.

“If you are im­muno-com­pro­mised, or if you are a per­son who is frail, or sick, then I would think a sec­ond in­fec­tion could po­ten­tial­ly be se­ri­ous enough to put you in the hos­pi­tal, but if you have a nor­mal im­mune sys­tem, the sec­ond in­fec­tion is not like­ly to be se­vere,” he added.

Ex­perts said a re­in­fec­tion would pro­vide some lev­el of im­mu­ni­ty against any po­ten­tial re­in­fec­tion in the fu­ture, but the best im­mu­ni­ty is the re­sult of a hy­brid im­mu­ni­ty.

Hy­brid im­mu­ni­ty is the re­sult of hav­ing been both in­fect­ed and vac­ci­nat­ed against the virus. Ac­cord­ing to re­search, this could gen­er­ate a “su­per-im­mune” re­sponse.

How­ev­er, there is a risk in the long term ef­fects of the in­fec­tion.

“Any­one who re­cov­ers from COVID stands or risk of de­vel­op­ing so-called Long COVID,” Dr Schaffn­er said.

“[And so far] we have no in­for­ma­tion, on whether sec­ond in­fec­tions are more like­ly to re­sult in Long COVID than first in­fec­tions,” he added.

How can the rate of re­in­fec­tions be slowed?

Ex­perts have said the cur­rent guid­ance in place to com­bat COVID-19 are still ef­fec­tive. The World Health Or­ga­ni­za­tion (WHO) has rec­om­mend­ed peo­ple get vac­ci­nat­ed.

It al­so ad­vised peo­ple to main­tain phys­i­cal dis­tance, avoid crowds and close con­tacts, wear a prop­er­ly fit­ted mask, clean your hands fre­quent­ly, and cov­er your mouth and nose when cough­ing or sneez­ing.

“We need peo­ple to keep [fol­low­ing] all these mea­sures,” Dr Ali Fat­tom said.

“Pre­cau­tions are very im­por­tant, not on­ly for the per­son it­self, but you don’t want to trans­mit the virus to oth­ers and put them at risk,” he added.