‘Im­mu­nity may be twice as high as be­lieved’

The Daily Telegraph - - Front Page - By Laura Don­nelly, Richard Orange and Henry Bod­kin

UP TO a third of healthy peo­ple with­out symp­toms of Covid-19 may have de­vel­oped im­mu­nity to the virus, in­ter­na­tional re­search sug­gests.

The re­sults in­di­cate pub­lic im­mu­nity could be as much as twice that iden­ti­fied by an­ti­body tests, mean­ing in­fec­tion hotspots such as Lon­don could be fur­ther along the path to herd im­mu­nity than was thought.

Un­til now, ef­forts to mea­sure levels of pro­tec­tion against coro­n­avirus have fo­cused on an­ti­bod­ies, which have proved an un­re­li­able mea­sure.

At the start of the pan­demic, the Govern­ment’s ad­vis­ers sug­gested at least 60 per cent of the pop­u­la­tion would need to be in­fected in or­der to achieve herd im­mu­nity.

In­stead, Bri­tain en­tered lock­down, on the ba­sis of pro­jec­tions sug­gest­ing al­low­ing such levels of dis­ease would leave the NHS over­whelmed. But a new study by Karolin­ska In­sti­tutet in Swe­den, the only Euro­pean coun­try not to en­ter lock­down, sug­gests im­mu­nity levels in those with­out symp­toms may be twice as high as was thought.

It comes as sta­tis­tics re­vealed one in seven chil­dren in Le­ices­ter has now tested positive for Covid-19, with levels tripling in the last month.

The Daily Tele­graph has es­tab­lished preva­lence is now at 15 per cent among un­der-18s in Le­ices­ter – roughly three times the rate in Eng­land over­all.

As well as mea­sur­ing an­ti­body levels, the Swedish re­search ex­am­ined levels of T-cell re­sponse. T-cells are a type of white blood cell that helps the im­mune sys­tem fight off viruses.

In to­tal, 30 per cent of the healthy blood donors stud­ied were found to have de­vel­oped “T-cell im­mu­nity” – twice the num­ber of cases in which an­ti­bod­ies were de­tected.

Sam­pling in the UK sug­gests around 7 per cent of peo­ple in Eng­land have de­vel­oped an­ti­bod­ies, ris­ing to 17 per cent in Lon­don. The new re­search sug­gests levels of “T-cell” im­mu­nity may be sig­nif­i­cantly higher.

The new study does not show what level of im­mu­nity is given by a T-cell re­sponse. But sci­en­tists are in­creas­ingly ex­cited about the role played by T-cells, as they believe it may ex­plain why some groups – in par­tic­u­lar chil­dren – ap­pear to be more im­mune.

Mar­cus Bug­gert, an as­sis­tant pro­fes­sor at Karolin­ska In­sti­tutet said: “What this means is we are prob­a­bly un­der­es­ti­mat­ing the num­ber of peo­ple that have some type of im­mu­nity.

“If it means that these in­di­vid­u­als are to­tally pro­tected, or if they’re go­ing to get a milder or asymp­to­matic dis­ease in the fu­ture, it’s hard to say.”

Prof Hans-gustaf Ljung­gren, the se­nior co-au­thor of the study, said: “Our re­sults in­di­cate pub­lic im­mu­nity to COVID-19 is prob­a­bly sig­nif­i­cantly higher than an­ti­body tests have sug­gested. If this is the case, it is of course very good news from a pub­lic health per­spec­tive.” He said al­though the Karolin­ska study was rel­a­tively small and yet to be peer-re­viewed, if its find­ings are repli­cated, they would ap­ply to any city. Lon­don, for in­stance, might have about 30 per cent im­mu­nity and New York above 40 per cent.

An­ders Teg­nell, Swe­den’s state epi­demi­ol­o­gist, lost cred­i­bil­ity at the end of May, when an­ti­body tests found just 7.3 per cent of Stock­holm’s in­hab­i­tants had de­vel­oped Covid-19 an­ti­bod­ies by the end of April. This was far short of the 25 per cent he had been es­ti­mat­ing.

But Prof Ljung­gren said the an­ti­body fig­ures in the Swedish cap­i­tal had now risen and while re­searchers had been very puz­zled with the low an­ti­body re­sponses, “now when we see sig­nif­i­cant T cell re­sponses in terms of per­cent­ages of peo­ple be­ing af­fected them, it makes sense”.

Mean­while, a Ger­man study has sug­gested that ex­po­sure to the com­mon cold could pro­vide some level of im­mu­nity to Covid.

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