Science - USA (2021-11-05)

INSIGHTS | PERSPECTIVES

science.org SCIENCE

mendations for face coverings or masks for
students have varied from none in the UK to
being mandated from 2 years of age in the
US. In England, community infection rates
in adults were generally higher than rates
in children, except when adults were in na-
tional lockdown while children continued
in-person schooling in November–December
2020 and March–April 2021.
A key question about school safety, how-
ever, relates to asymptomatic infections and
their role in transmission. In adult institu-
tional settings, especially care homes, by the
time an outbreak was identified, a high pro-
portion of residents and staff had already
been infected, with 30 to 60% infected by
the end of the outbreak. Reassuringly, an-
tibody seroprevalence studies in schools
have consistently reported similar or lower
seroconversion and seropositivity rates in
students and staff compared to local com-
munity rates, most likely contributed by the
mitigations in educational settings ( 4 , 9 ,
10 ). Reasons for lower transmission by chil-
dren compared to adults remain uncertain
but include higher rates of asymptomatic
infection, smaller lung capacity, and shorter
duration of viral shedding than in adults.
That infection and outbreaks occur in ed-
ucational settings is undeniable and likely
reflects a combination of factors, including
local community infection rates and inad-
equate in-school mitigations. Additionally,
where wider testing has been performed,
transmission to household members of
staff and students can also occur ( 11 ), high-
lighting the importance of early and rapid
contact tracing and isolation to control
virus transmission. The number of mitiga-
tion measures, rather than individual mea-
sures, are important in preventing in-school
transmission ( 12 ). Although the risk of se-
vere COVID-19 in children and their house-
holds is low ( 13 , 14 ), concerns remain about
Long Covid in children, which can be debili-
tating. The risk of Long Covid has been dif-
ficult to estimate because of the wide range
of symptoms and varied surveillance meth-
odology, but ranges between 2 and 14% in
children compared to 20 to 30% in adults.
The emergence of more transmissible
variants of concern, first Alpha and now
Delta (B.1.617.2) , poses additional challenges
for educational settings. Increasing infection
rates in unvaccinated populations, including
children, result in widespread educational
disruption because of cases and class bub-
bles self-isolating at home. In the UK, >10%
of students were absent from school in July
2021 when the Delta variant was circulating.
Notably, although the number of children
hospitalized with COVID-19 increased with
the Alpha and Delta waves, hospitalization
rates in children with confirmed COVID-19

remained stable, suggesting that these vari-

ants are not associated with more severe

disease in children. The recent licensure of

highly effective vaccines, however, is already

changing the landscape of the pandemic

and should allow schools to reopen safely

worldwide. Most high-income countries are

now offering COVID-19 vaccines to children

aged 12 years and older even though their

personal risk of severe disease remains very

low. Vaccinating adults, however, will pro-

tect staff and household members against

COVID-19, and the attendant lower commu-

nity infection rates should confer indirect

(herd) protection that will help reduce infec-

tion risk in children ( 15 ).

In their recent updates on the role of

schools in transmission and COVID-19 in

children, the European Centre for Disease

Prevention and Control (ECDC) and US

Centers for Disease Control and Prevention

(CDC) have reported that, when adequate

mitigation measures are in place, transmis-

sion in schools is usually similar to or lower

than community transmission. Therefore,

although school closures may contribute

to reducing transmission, by themselves,

they would be inadequate in prevent-

ing community transmission and, conse-

quently, the benefits of in-person schooling

outweigh the risks, especially in countries

where adults are fully vaccinated against

COVID-19. The focus now must be on as-

sessing and implementing evidence-based

mitigations to reduce the risk of infection

in schools not only to protect students and

staff but also to minimize disruption to edu-

cation and access to additional services. j

REFERENCES AND NOTES

1. C. Signorelli, A. Odone, Int. J. Public Health 65 , 1435
   (2020).


2. S. Ismail et al., Lancet Infect. Dis. S1473, 30882 (2020).


3. A. A. Mensah et al., J. Infect. 82 , 67 (2021).


4. S. N. Ladhani et al., Lancet Child Adolesc. Health (2021).


5. F. Aiano et al., Lancet Europe 10.1016/j.
   lanepe.2021.100120 (2021).


6. K. O. Zimmerman et al., Pediatrics 147 , e2020048090
   (2021).


7. A. Falk et al., MMWR Morb. Mortal. Wkly. Rep. 70 , 136
   (2021).


8. J. K. Varma et al., Pediatrics 147 , e2021050605 (2021).


9. S. N. Ladhani et al., EClinicalMedicine 37 , 100948
   (2021).


10. Office for National Statistics, https://www.
    ons.gov.uk/peoplepopulationandcommunity/
    healthandsocialcare/conditionsanddiseases/
    bulletins/covid19schoolsinfectionsurveyengland/
    round5englandmay2021


11. M. Okarska-Napierała, J. Mańdziuk, E. Kuchar, Emerg.
    Infect. Dis. 27 , 317 (2021).


12. J. Lessler et al., Science 372 , 1092 (2021).


13. H. Forbes et al., BMJ 372 , 628 (2021).


14. R. Wo o d et al., Arch. Dis. Child. archdis-
    child-2021-321604 (2021).


15. R. J. Harris et al., N. Engl. J. Med. 385 , 759 (2021).

SUPPLEMENTARY MATERIALS

science.org/doi/10.1126/science.abj2042

10.1126/science.abj2042

IMMUNOLOGY

A helminth-

induced

antimicrobial

protein

By Nicola Harris and

Lakshanie Wickramasinghe

A

ntimicrobial proteins (AMPs) con-

stitute the first line of host defense

against invading microorganisms.

Both immune and nonimmune cells

can deploy a diverse array of AMPs

to combat specific pathogens ( 1 ). This

forms part of an evolutionarily conserved

mechanism within the host to rapidly kill and

neutralize infectious microbes that breach

barrier tissues, including the skin, lungs, and

intestines ( 2 ). Not only are AMPs constitu-

tively expressed, but they can also be induced

by an inflammatory stimulus ( 1 ). On page 710

of this issue, Hu et al. ( 3 ) identify small pro-

line-rich protein 2A (SPRR2A) as a distinct

AMP with antibacterial properties against

Gram-positive, but not Gram-negative, spe-

cies. SPRR2A maintains intestinal barrier

integrity during homeostasis and limits infec-

tion with the Gram-positive bacterial patho-

gen Listeria monocytogenes. Intriguingly,

SPRR2A also plays a distinct role in protect-

ing the intestines from bacterial invasion dur-

ing helminth (parasitic worm) infection.

In vitro experiments by Hu et al. revealed

that SPRR2A exerts its antimicrobial proper-

ties by binding to negatively charged lipids

on bacterial membranes, effectively killing

these microorganisms. The authors found

that SPRR2A is expressed by intestinal epi-

thelial goblet and Paneth cells in response to

the bacterial colonization of germ-free mice.

The generation of SPRR2A-deficient mice re-

vealed an expansion of Gram-positive bacte-

ria within the small, but not large, intestinal

lumen and mucus layers, consistent with its

selective antimicrobial activity against Gram-

positive bacterial species. The optimal activ-

Small proline-rich

protein 2A regulates the

intestinal microbiota

Department of Immunology and Pathology, Central Clinical

School, Monash University, Melbourne, VIC, Australia.

Email: [email protected]

682 5 NOVEMBER 2021 • VOL 374 ISSUE 6568