Characterization of the humoral immune response to BNT162b2 in elderly residents of long-term care facilities five to seven months after vaccination

27 T he eld erly re sidin g in l ong -term c are f a cil it i e s (L TCF s) are a g roup at hig h r i s k f or C O VI D -19 . H e n ce, 28 mo nitor i ng of t h e va cc ine -ba sed i mmunity ha s a pivotal rol e i n iden tify ing st rategi e s t o pr o vid e 29 op t i mal pr o tec tion i n thi s p opul at ion. We exa mined the i mmune re spon se to the mRN A v acc ine 30 BNT16 2b2 ag ain st C OVI D-19 fiv e to seve n month s a fter c ompl eting a two -do s e re gi men. 31 We de te r mi ned signi fic antly lowe r a n t i-S ARS- Co V-2 anti bod y ti ter s in 298 S A RS -C oV -2 naïv e r e s i den t s 32 w ho we r e a t le a st 75 y e ar s o f ag e ( me an 51.6 0 BAU/ml) (med i an ag e 87 y ear s , r a n ge 75 to 101 y e ar s) 33 w hen compa r ed to h e alth c ar e worker s (H CWs) a g ed 18 to 70 years (m ea n 156 .99 BAU/ml, p < 34 0 .001). O f the S ARS -Co V-2 naïv e re side nts , 29 had d etec t a ble neu tr a lizing an t ibodie s a gain s t th e 35 Del ta v arian t (9.5% ), and 14 o f tho se (4 8.3%) only had a bord erlin e tit er o f 1:1 0 . Of 114 H CWs, 36 36 (31 .6%) h a d d etec tab l e neu trali zing an ti bodie s. In a group of 14 eld erly re side n ts who had h a d a P CR -37 c onfirmed bre ak t h r o ug h inf ec t io n , th e mean a n t i body ti ter wa s signi fic an tly hi gher th an in the o t he r 38 tw o g r oup s (3199.65 BAU / mL ) (p < 0.0 01), and 12 (85 .7% ) had d et ec tabl e ne utralizing an tibodi e s 39 a gains t th e Del ta v aria nt. 40 Our da t a de mon stra te t ha t 90 .5% of el de r ly re sid ent s o f LTCF s had no d et ect able neu trali z ati on-41 c ompeten t an t ib odie s agai n s t t he dom in ant Del ta va r i an t five to sev en mon th s af ter vac cina t i o n, and 42 tha t neu tr a li z i ng an tib ody tit er s we re re sto r e d foll ow ing a b reak -th rough in f ection. O u r r e sult s 43 sugg e s t th at bot h r e s ide n ts and hea lt h c are worke rs in LT CFs w ould bene f i t fro m a booste r v acc ine 44 six month s a ft e r comple t i ng the two -do s e sche dule or ea r l i er. 45 46 47 48 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint

49 Adv ance d age is a s tr ong risk f a ctor for s eve r e and f atal di s e a s e when inf ecte d w ith SARS -Co V -2. 1–3 I n 50 the eld e r l y, in co ntr ast to c hild ren and youn ger a dult s , co r on a viru s di se a se of 20 19 (C OVI D -19) i s 51 rarel y a symptoma tic 4 , and re spi rat or y fai lure a nd org an d ysfunc ti on are p re sen t i n ma ny hospit alize d 52 pa tien t s . 5,6 T here fo r e ol der adult s were design a t e d a high priori ty to be v acc ina t ed in the roll -ou t of 53 CO VI D-19 va cc ine s . 7 54 Due to incre a sed ex po s ur e to t he v iru s , livi ng in long-term care f ac iliti es (L T CFs ) fur ther incr ea se d 55 C O V I D - 1 9 - r e l a t e d m o r t a l i t y i n t h i s g r o u p o f p a t i e n t s 8 . In Europ e, 30 to 60% of al l C OVI D-19 -r elat ed 56 de ath s we re att r i but ed to re s id ent s o f L TCFs du r in g th e early pa ndemic . 9 Earl y COVI D -19 v acc ine 57 stu die s found a high e ffic ac y in a dult s 10,11 , but the elde r ly , e s p e cia lly wi t h c omo rbiditie s and frail ty, 58 w ere c ommonly underre pre sent ed or e xcl uded. 12 59 Wan ing imm unity due to immuno se ne sce nce can lea d t o imp aired immuni ty i n the se hig h-ris k 60 pa tien t s .13 Vac cin e -induc e d a n t i bodi e s in the elde rly di splay l ower p r o tec tive capa city, an d T-c ell 61 re spon se i s s k ewed tow ard s shor t-l ived ef fec t ors.14 I n cas e of CO VI D-19 , th e vac cin e is u s ua lly g iven 62 to e st abli sh novel immu nity r a t he r than boos ting pre -exi sting immuni t y , whic h i s th e ca se in mo st 63 v acc ines appli e d i n t h e e lde rly. Alth ough fir st r eal -w orld C OVI D-19 va cci ne e f ficac y data hav e be e n 64 fa vorabl e, ef fic acy a gain s t ho s pi tal iz a t i o n a nd d eath was l ower in t h o s e 80 ye a rs of a ge a nd old e r 65 w hen c ompared t o 6 5 to 79 y ear s o f age. 15 66 T he emerge nce o f novel v arian ts o f conc ern, mo st r e c ently t h e D e l ta varia n t , and the c once r n s abou t 67 w aning i mmunity aga inst symp tomatic an d s eve r e CO VI D -19 r a i sed a di scu s sio n on t he n e ed for a 68 bo oste r sho t. But th ere is unc e rtain ty re garding the ef fec t o f a ge an d fr a il ty o n immunity aga in st 69 s e v e re C O V I D - 1 9 a f t e r v a c c i n a t i o n . 70 I n thi s s t u dy, we s oug h t t o de termin e wh ether marke rs of humoral and cel lu lar immu nity di f f e r 71 sign ific antly be t w een old er adul t s ( ≥75 ye ar s of a g e), a nd a cont rol group o f h eal t h c a r e w or k er s 72 (HC Ws) s ix months a fter vac cina ti on a nd ana lyzed th e a ssoc iati on of multi pl e va r i ant s , incl uding 73 me dica t i on an d mu ltimorbidi ty, on t h e immune r e s pon se . 74 75 76 77 78 79 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint

80 Recruitment of study participants and inclusion criteria 81 Th i s is a no n - in t er v e n t i on al o bs er vat o r y s t ud y. T h e H ess i a n M i n ist r y f o r S o c ia l A ffa i r s an d I nt e g ra t i on 82 c ommissi oned thi s study and appr oa c hed long -t erm c a re provi de rs in H es se w it h suit able 83 c harac t e r i stic s t o par ticip at e in th e s t u d y. All pa r tic ip ant s wer e in formed a bout th e aim of the st udy, 84 a nd writte n i nfo r me d con sen t wa s obt a ined fr om eith er th e s tudy par ticip ant s them selve s or f ro m 85 the leg al guardia n in c a s e one h a d be en a ppoint ed. Bl ood s a mpl e s and d a ta w ere colle cted at the LT C 86 fa cili t i e s . T hr e e group s o f s t udy par tici pa nts w e re formed . 87 T he comple t e two -do se s c hedul e of BNT162b2 (Comirna ty, Bio N Te ch / Pfize r ), ap pli ed at t h e 88 rec ommende d tim e in terval of 21 d ays , had t o be compl et ed fiv e t o s even m onth s b ef ore bloo d 89 c ollec tion r egardl e s s o f the s tudy group. F ur the r inc lu sion cri teri a f or s tudy p a r ti c ipant s in th e mai n 90 stu dy group ( group 1 ) of S ARS -Co V -2 naï v e res i den ts in L TCF s for th e eld erly i ncl ude d age o f a t le a s t 91 7 5 yea rs at the da y o f th eir fir s t vac cinati on . All pa rtic ipan t s wit h a k nown and co nfir me d SARS - Co V- 2 92 i nfecti on in th e pa st o r a po s i t i ve an ti -S ARS- Co V-2 n uc leoc ap s i d a n t i body t e s t were ex clude d from 93 the main ana ly si s . I n ad dition , tw o co ntr ol group s wer e a l s o rec rui t e d: HC Ws in L TCFs fo r th e e lderl y 94 be t w ee n t he age s o f 18 a nd 70 y ear s we re r ec r ui ted t o t he fi rst co nt r ol g r o u p ( group 2 ). H CWs with a 95 k nown SARS -C o V-2 in fec tion in the pa s t o r a po sit i ve an ti-S ARS -C oV -2 n uc leoc a ps i d an tib ody t i te r 96 w ere ex clude d . The sec ond c on t r ol g r o u p ( group 3) was c o m p r is e d o f r es i de n ts of t he a ge of 7 5 ye ars 97 or old er with a s ub s eque n t , PC R-c on firm ed S ARS - CoV -2 b r e ak through inf ec t i o n no e a r li e r th an 1 4 98 da ys a ft er th e s econd vac cina t i o n. 99 Markers of the humoral immune response 100 Anti -S A RS - Co V-2 Nu cleoc ap sid A ntibody Assay 101 T o determin e whe t h e r a pr e viou s inf e c tion w ith S ARS- Co V -2 ha d oc curred , s erum sampl e s were 102 te st ed for the pre se nce of a n t i - S ARS - Co V-2 nuc le oca p s id antib odie s. W e us ed th e Abbot t ARCHI TECT 103 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint S ARS- Co V -2 IgG te s t (A bbot t L abor ato ri es . Abb o t t Pa rk, Illin o is, USA ). D e tec t ed antibodi e s may be 104 e lici t e d a ft er in fecti on , bu t not va cci nati on wi t h an mRNA va cci ne. 105 Anti -S A RS - Co V-2 Spik e IgG An tibody A ssa y 106 S erum s amp le s w e re te st ed for the p re senc e o f ant i-S ARS -Co V - 2 S pike Ig G an ti bod ie s . F or thi s , we 107 use d the Advis eDx SARS - CoV -2 Ig G II as s a y on t he Abb ot t A l inity i® pla tf orm (Ab bot t La b ora tor i e s , 108 Abbo tt Park, Illi noi s , USA ). This a ssay d etec ts an tibodi e s ta rget ed sp ecific ally a gains t th e r ec ep tor-109 bi nding d omain of S ARS -C oV -2. The r e s ul ts ar e pr ovid ed in s tand ardiz ed bin ding a ntib ody uni t s ( BAU) 110 pe r m l. A r e s ul t of l e s s t h an 7 .1 BA U/ m l was con side red n egativ e, and a re sult o f 7.1 to 8 .51 BAU/ml 111 w as con sider ed po sitive . De tec ta ble an ti bodie s may be elic ited a ft er bo th infe c ti on and va cc ination 112 w ith an m RN A v acc ine. 113 Neut raliza tion a ssay again s t the Del ta v a riant 114 S erum sample s w er e fu rth er ana l yz e d for t he pr e senc e o f a n t i bodi e s wi t h neutr alizing c apa city 115 a gains t th e D elta va rian t of S ARS- C oV -2 (B.1 .617.2 ) in a b io sa fe t y l evel 3 labora tory. Th e 116 me t h odol ogy of the S ARS - C o V-2 neu tr a li zation a s s a y ha s be en de scrib ed el sewh e re. 16 117 I n br i e f, serum s ample s wer e se rially dil uted (1:2 ) and inc ubat ed w it h 4000 TC I D50/mL o f t he Del ta 118 v ariant o f SARS -C oV -2 ( B.1.617 .2) for o ne hour pr i or to in fe c tion o f Ca Co -2 ce lls. A fte r 48 hour s 119 i nocula t i on i nf ected c ell s we r e e xamin e d for c yto pathic ef fec t ( CPE ) f ormat ion b y light mic r oc opy to 120 d et e r m in e t he n e u t r a l iz a t i on t it er . 121 Clinical parameters and patient history 122 I t e m s w ere reco rded i n an in tervi ew w it h eac h s tudy p articip ant and de r iv e d fro m the pa tie n t hi s t ory 123 form with con sent o f t he pa t i en t, or le ga l g uardian if one had bee n app oint ed . Study partici pan t s 124 from the H C W -g roup p rovid ed inf or m at ion on t he i tem s th em selve s. The se it e ms w er e: (i ) da t e o f 125 bi r th (ii ) da te s of vac cina ti on w ith BN T162B 2 (iii) curre nt heig h t and weig h t (iv) known medic al 126 di agnos e s (v) c ur r ent me d icatio n. 127 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Statistical analysis 128 Dat a ana ly s i s w a s p erform ed u s i ng RS tudio Ve r si on 1.4 .1717 . Mean An ti-S A RS -C oV - 2 s pi k e Ig G 129 a ntibody tite r s w ere te sted fo r normali t y (S hapiro -Wilk te s t), and homog e nei ty of va r i a nce b e t w ee n 130 the thr ee study group s r e sp ec t i vely (L eve ne’ s te s t) T he th r e s hold for s ta ti stica l sig nifica nce w as α < 131 0 .05 in tw o- s id e d t - t es t s . 132 Funding source and ethical approval 133 T he stud y wa s c ommis s i oned and fund e d by t h e He ssian Mini s t ry o f Soci al I ssue s a nd Integ rati on. 134 T he study pr o toc ol h as be en appr ov ed by the e thic s boa rd o f th e Unive rsi ty Ho s pit al Fr ankfur t ( No . 135 2 0-864) and h as b een r eg iste red on t he Ger m an Clini cal Trial R eg iste r (D RKS00 025813). 136 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint

137 Study population 138 S ample s w ere col lec ted from 2 2 nd Jul y to 16 th S eptemb er 202 1 in 16 LTCF s in H ess e, Ge rmany . 139 Group 1: Residents of LTCFs ≥ 75 years of age without prior infection or 140 breakthrough infection 141 A tota l o f 298 re s i d ent s o f th e LT CF s par ticip at ed in t h e s t udy and wer e i nclude d in group 1 . 142 2 12 (71.1% ) were f emal e , 86 (28.9 %) we re ma l e, a nd n on e r epor t e d non -bina ry g ender. The m edian 143 a g e w a s 8 6 y e a r s ( r a n g e : 7 5 t o 1 0 1 y e a r s , I Q R : 8 2 t o 9 0 . 8 y e a r s ) . T h e m e a n Bo d y M a s s I n d e x ( B M I ) 144 w as 25.6 k g/m 2 r a nging from 14.9 k g/ m 2 to 42.9 k g/ m 2 . 145 Group 2: HCWs aged 18 to 70 years of age 146 1 14 HCWs we re inc luded in g r o up 2. 8 3 (77.8%) were f emale , and 31 (27.2% ) we r e mal e . Non e 147 repo rted non -bi n ary gende r. T he media n a ge wa s 53 y ear s ( rang e: 24 t o 70 yea r s, I QR: 45.3 to 59. 8 148 y ear s ). Th e mea n BM I wa s 2 6.8 kg / m 2 ra ng ing from 18 to 50 k g/ m 2 . 149 Group 3: Residents of LTCFs ≥ 75 years of age with breakthrough infection 150 1 4 r e s i d e n t s o f t h e L T C F s w e r e i n c l u d e d i n g r o u p 3 . 1 3 w e r e f e m a l e ( 9 2 . 9 % ) , o n e w a s m a l e ( 7 . 1 4 % ) , 151 no ne re ported n on -bi nary gend er . The me an numbe r o f da y s be t w een the se c ond va cci nation and 152 the po s itiv e P CR t e st r e s ul t w as 109 day s. The ea r l ie st brea k thr o ugh in fec ti on hap pe ned 19 da ys, an d 153 the la te s t 2 11 day s a fter the sec ond va cc ination . Th e me dia n age was 89 y ear s (ra n ge: 82 to 93 ye ar s, 154 I QR: 86 .3 - 91). T he m ea n BM I was 24 .24 kg / m 2 rang ing from 17 t o 32 kg / m 2 . 155 Table 1 pr ov ides an o ve rview of th e stud y pa r tic ipant s in al l thr e e group s . 156 Markers of the humoral immune response 157 Of the study par tici pan t s in group 1 (re s ide nts ≥ 75 yea rs o f ag e with out know n prior in fec t i o n o r 158 brea kth rough in fecti on) , 6 (0 . 02%) had d etec tabl e SARS -Co V-2 nuc l eoca p s i d a ntibod ie s and wer e 159 e xcl uded from t h e pr i ma ry ana ly si s . In g r ou p 2 (HCWS a ged 18 to 70 y ear s w ith out a pri or i nf ectio n 160 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint or bre akth rough in fec t io n ) no par t i cipa n t had de tect abl e S A RS - CoV -2 nuc leoc aps i d an tibo die s . In 161 g r ou p 3 , whic h wa s compri s ed o f resi de nts with a P CR -c onfi r m ed b r e akt hrough infec ti on, o nly 4 o f 162 1 4 particip an t s (28 .6%) h a d de tect abl e a nti-S ARS -Co V - 2 nucl eoca p s i d a ntib odie s. 163 5 0 partic ipan t s (16 .78% ) in grou p 1 t e s t ed nega tiv e for a n t i -S ARS - Co V-2 spik e IgG a nt i bodi e s, 9 164 (3. 02%) had a bo rde rline po sitive r e su lt and 2 39 (80.2% ) te ste d po si tive. I n t h e fi r s t con trol group o f 165 HCW s (gro up 2), a v a st m ajo rity of 97 .3 7 % (111/114 ) o f par t i cipan ts te sted po s i t i v e. Tw o partici pan t s 166 te st ed nega t i ve, and o n e te sted bo rderli ne po s itiv e. In the se cond c ont r ol g r o up of r e sid ent s with a 167 brea kth rough inf ectio n (group 3 ), all 14 participa n ts t e sted po si t i ve fo r anti -S ARS - CoV -2 spike Ig G 168 a ntibodi e s (14/14 ) ( figure 1 ) . 169 I n group 1, th e an ti-S ARS -Co V -2 s p ike IgG anti bod y c once ntrati on had a me a n of 51.60 BAU /ml 170 (rang e : 0.90 – 710. 64 BAU /ml , I Q R: 1 2 .0 9 – 6 1.47 B AU / ml ). Thi s wa s lo wer t han i n group 2, w hic h had 171 a mean o f 156. 99 BA U/ ml ( r a nge : 5. 6 1 – 2 008.16 BAU/ml, I Q R: 57 .04 – 176.29 BAU/ml). Th i s 172 di ffe re nce was st ati s tic ally signific an t ( CI 95% , p < 0.0 01) ( figures 1-3) . In th es e group s , a linea r 173 de clin e wit h ag e wa s ob s erved, w hich w as more promin ent in gr oup 1 (CI 95%, p < 0 .001) ( figure 1 ). 174 I n group 3, the me an anti body c once ntr ation o f a n t i -S ARS -C oV -2 RBD Ig G was hi ghe st, with 31 99.65 175 BAU/mL (range : 58.73 – 11360 .00 BAU /ml, I Q R: 857 .65 – 4601 .8 8 BA U /ml ). Th i s i s signi fi cantly highe r 176 tha n in group 1 and g r o u p 2 (C I 95 %, p < 0.001, r e s pe c tivel y). 177 Neut ralizing an tibod i es ag ain st th e De lta v ariant wer e det ect ed in 29 s t udy pa r tic ipan ts (9.7% ) o f 178 g r ou p 1, of w hich 14 (48.3% ) had a b or d erlin e po s itiv e tite r o f 1:10 . In grou p 2 , 36 partici pant s 179 (31 .6%) ha d de tect abl e ne utr alizing a nti bodie s aga in st th e D e l t a varia n t , o f whic h 16 w er e borderlin e 180 po s i tiv e ( tit e r o f 1 :10) . In g r oup 3, re s i den t s w ith a br eak t h roug h inf ec t io n , 12 (85.7 %) ha d 181 de t e c table ne u t ral iz in g antibo die s aga in s t the D e l ta vari ant , of whic h none we r e bord erline ( figure 182 4 ). 183 184 185 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint

186 Here, we r epor t the ana ly si s o f mark er s o f t he hum oral re s pon s e fiv e t o seven month s a f t e r 187 v acc ination with the mR NA va cci ne BNT 162b2 in a g r ou p o f r e s ide n ts of L TCF s. The SA RS- Co V -2 na ïv e 188 re siden t s, age d ≥ 75 y ear s o f age, had a s igni fican t ly lowe r conc en tr a t io n o f anti -R BD -antib odie s th an 189 y ounger hea lt h H CW s ( figures 2 and 3). A linear dec lin e w ith age w as ob se r v ed i n both the grou p of 190 re siden t s and HC W s but wa s more ma r k ed in t he el derly ( figure 1 ) . 191 T he elde rly al so h ad a small er fr action o f indi vidual s wi th de t e ct able ne u t ral iz in g antibodi e s aga in st 192 the Del t a varian t (9.7% , figure 4) . Almos t half (48.3% ) of t hi s mino r ity with det ec t a ble neu trali zati on 193 on ly e xhibi t e d a bo rde rline po s i tiv e ti t er o f 1:10. Wh ile th e mean anti -SAR S -Co V-2 Ig G a n tibody 194 c once ntratio n i n our c o ntrol grou p o f y ounger H CW s wa s signific antly hi gh er, n eutr alizati on aga in s t 195 the Del ta v arian t wa s al so only detec ted in a minority of 31.6% of t he part i cipa n t s in thi s group fiv e 196 to s eve n month s a f ter havi ng c omple ted a full seri e s of vac cina t i on. 197 A b r e a kthr ough inf e ctio n v a s tly incr ea s e d bot h t h e anti body conc en tra tion and f r ac tion o f ind ividu a l s 198 w ith d etec table Del ta- neu trali z ing a n t ib odie s am ong t he el d erly study partic ip ant s , dem on stra ting 199 rec overabi li ty of the humora l immun e re s po n se. 200 T hese dat a sup port th at a b oo st er v acc ine w ould be be ne f i cial in thi s hi gh -r i s k g r ou p o f p a t i ent s six 201 mo nt h s or ea rlie r a ft er co mpl eting th e two -do s e sche dul e wi t h a n mR N A v acc ine. T hi s i s i n 202 c oherenc e with oth er studie s in thi s a ge gro up, ev en though s t ud ie s ba sed on p seudov iru s 203 ne utra liz a t i on a ssays prov ided dive r g en tly higher rat es o f neu tr a liz atio n. 17 A pos sibl e expl anati on 204 mi ght be th at for th e neu traliz atio n a s sa ys w e employ ed an auth entic D e l t a va riant i sol at e 16 r a t h e r 205 tha n a p s e udoviru s . Clinic al i sola te s har bor additio nal mut a t i on s out sid e the Spi ke region w hich c an 206 i mpact th e v iral fi tne s s or s en sitivity to a n t i bodie s in ce ll cu ltu r e . M arker s o f t h e cell ular re s pon s e o f 207 the study p a r tic ip ant s ar e cu rren tly exa mi ned and will b e publi sh ed w h en av aila bl e. Th e se ad diti onal 208 da ta may influ enc e th e i nte r pr et ation o f t he s tudy re sult s. 209 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint S ince a majority of HCW s from the s e f ac ilitie s, a group at l arg e risk of t ran smi t ting infe c tion t o 210 v ulnerable pa tien ts, al so d id not have d e t e c table ne u t ral i z in g an tibodi e s ag ain s t the D elt a v aria nt, a 211 bo oste r of the hu mora l re s p o nse app ear s indic a ted in t hi s g r ou p a s well . 212 Of the s tudy pa r tic ip ant s i n group 3 , all of whic h h ad had a P CR - c on firm ed br ea kthrough i n fec tion , 213 on ly 28.6% had detec t a ble anti -nuc l eoc a ps i d Ig G re spon s e. Thi s highli ght s that infec t i on with SARS -214 Co V-2 in thi s g r ou p ma y occ ur wi t hou t mounting a n a nt i - n ucl eoc ap sid r e s p on s e, and some o f the 215 othe r p a rtic ipant s may al so hav e h ad a n unknow n infec tion th at we n t un detec ted . A d di tional 216 l imitation s of our s tudy inc lude tha t br ea k- thr oug h i nf ection s in g r ou p 3 oc cur red a t div er se tim e 217 po int s be fore bl o od sa mple s were tak en . In ad dition t o age , immunoge nicity and effic acy of vac cine s 218 ma y be influe nced a nd s upp re s s e d by se veral f ac t o rs , incl uding other medic al co ndition s, a n d body 219 c omposi tion w it h a ve r y low or high BMI . 18 220 Ana lys e s of the s e fact or s in our st u dy coh or t w ill be provid ed in a su bs eque nt pu bl ication . 221 222 223 224 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Tables 225 Table 1: Characteristics of the study participants 226 227 228 229 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Figures 230 Figure 1: Anti - SAR S-C o V- 2 spik e IgG ti ter (loga r i thmic ) by study part i cip ant s’ ag e. 231 Group 1 (r e sid ent s o f L TC F s ≥ 75 yea rs of age ; orang e ), grou p 2 (H CW s a t L TC F s, 18 to 70 yea rs o f 232 ag e; bl ue ), g r ou p 3 (re s ide n ts of L TC F s aft er a b rea kt hr o ugh in fect ion, gre en ). P lot ted withi n t h e 233 s c a tt er is t he l i ne ar r e gr es s io n ( l i n es i n co l o rs o f t h e r es p e c t i v e s t u d y g r ou ps ) w ith t h e st a n da r d e r r or 234 (grey are a s, 95% C I ). The r ed line displays th e c ut - o f f an ti - SARS - Co V- 2 spike Ig G anti body 235 c oncentr ation of 8 .52 BA U/ ml, whi ch i s con sid ered a po s itiv e te s t r es ult (bor derline : 7.10 - 8.5 1 236 BAU/ ml ). 237 238 239 240 241 242 243 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint 244 245 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Figure 2: Anti - SAR S-C o V- 2 spik e IgG an ti bod y tite rs (lo gari thmic) b y group. 246 L ogarithmic de picti on in box plot s, 95% C I an d I QR (25%- 75% ) o f group 1 (r e s i d e nts o f L TC F s ≥ 75 247 ye ar s of a g e; or ange ) , group 2 (H C W s a t L TC Fs, 18 to 70 yea rs o f ag e; blu e) , a nd g roup 3 (r e siden t s of 248 L TC Fs a ft er br eakthr ough inf ection , gree n). St ar s rep re s e n t ou t l ier s. 249 250 251 252 253 254 255 256 257 258 259 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Figure 3: Anti - SAR S-C o V- 2 spik e IgG an ti bod y tite r (non - loga r ithmi c) . 260 Violi n plo t s fo r v isualiz atio n of di ff er enc e s in th e di stribu tion o f an ti- S A R S - CoV - 2 spi ke Ig G anti body 261 tite r s o f grou ps 1 (r e s id e nts o f L TC F s ≥ 7 5 years o f ag e ; orange ) and 2 (H C W s a t LTC F s, 1 8 to 70 y ear s 262 of a ge; bl ue ). The re d l ine di splays the cu t- o f f anti - SA RS-C o V - 2 s pik e IgG a n t ib ody c oncentr ation o f 263 8.52 BAU/ml, w hich is con side red a po s i t iv e te st res ult ( bord erline : 7.10 - 8 .5 1 BA U /ml) . 264 265 266 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Figure 4 : Ba r pl ots depic t i ng the frac tio n of s tudy pa rtic ipan t s in group 1 (re si dent s o f LT CF s ≥ 75 267 y ear s of a ge ), group 2 (HC Ws at LT CF s, 18 to 70 yea r s o f age), a n d group 3 (re s i de nts of LT CF s a fte r 268 brea kth rough i nfe ction ) w ho ex hibit n e utral iz a t i o n ti ter s again s t the D el t a va r ia nt five to seve n 269 mo nt h s af ter rec eiving th e s econd do s e of an mRN A va cc ine. 270 271 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Acknowledgments 272 T he autho r s thank the st af f o f the fac ili t ies we v i s i ted , for th eir aid i n c onductin g our in ves t i gatio n, 273 a nd thei r tir ele s s work in t he p andem ic a nd beyo nd. 274 We al so th ank a ll re sid ent s and s t a f f who don ated bl ood fo r thi s stu dy. 275 276 Potential conflicts of interest 277 S .C . rece ived h onora rium fo r se r v ing on a c linic al adv isor y bo ard f or Bio NTec h. 278 279 280 All rights reserved. No reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for thisthis version posted November 10, 2021. ; https://doi.org/10.1101/2021.11.09.21266110doi: medRxiv preprint Literature 281 282 1 . 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