High and increasing SARS-CoV-2 infection prevalence amongst school-aged children in England

The latest round of the REal-time Assessment of Community Transmission-1 (REACT-1) study indicates that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread among children.

Study: REACT-1 study round 14: High and increasing prevalence of SARS-CoV-2 infection among school-aged children during September 2021 and vaccine effectiveness against infection in England. Image Credit: Yau Ming Low/ ShutterstockStudy: REACT-1 study round 14: High and increasing prevalence of SARS-CoV-2 infection among school-aged children during September 2021 and vaccine effectiveness against infection in England. Image Credit: Yau Ming Low/ Shutterstock

Background

The coronavirus disease 2019 (COVID-19) pandemic caused much harm to the UK during its first and successive waves. This prompted among the earliest COVID-19 vaccine rollouts in the world, beginning in December 2020. This prioritized the high-risk population comprising the elderly, healthcare workers, and those with certain health conditions that put them at risk of severe COVID-19.

The third wave, which began towards the end of May 2021, was driven chiefly by the introduction of the Delta variant of the virus in September 2021. The COVID-19 vaccination effort was extended to 12-15-year-olds and a booster dose in individuals aged 50 years or more, health and social care workers, and high-risk people younger than 50 years.

Despite a drop in the daily number of vaccinations, almost 80% of those above 12 years had got two doses of the vaccine.

What did the study show?

As schools reopened in September 2021, allowing free intermixing of children rather than bubble groups and without contact tracing by schools, the incidence of cases of COVID-19 confirmed by reverse transcription-polymerase chain reaction (RT-PCR) also rose slowly.

The results of round 14 of the study are available as a preprint on the medRxiv* server. They demonstrate that from June 24 to September 27, 2021, in rounds 13 and 14, the prevalence of COVID-19 remained stable or rose among children aged 5-12 years and 13-17 years.

The prevalence was 2.3% and 2.6% in children of these two age groups, respectively. All the samples were positive for the Delta variant or its sub-lineages, and in one sample, the E484K escape mutation was also detected.

An overall prevalence of 0.8% was observed in round 14, up from 0.6% in round 13, even with potentially less sensitive sample handling in the former case. By age, the least prevalence was 0.3% in those aged 75 years or more; conversely, it was 2.6% among those aged 13-17 years.

In the under-18 group, the reproductive number R was 1.18, indicating a growing epidemic. Conversely, the R-value of 0.81 indicated its decline among the 18-54-year-olds.

In round 14, the key contributors to increased prevalence included age, geographical location, being an essential worker, and household size. Larger households had higher prevalence rates, 0.33% to 1.75% for single-person households. Households with children also had higher prevalence rates at 1.4% vs. 0.4% for childless households.

The odds of acquiring infection were thus 1.8 times higher and 2.4 times higher, with households containing up to five and six or more members, respectively, relative to single- or two-member households.

The highest prevalence was among contacts of a confirmed case, at 7.4% vs. 0.4% among those without a history of contact.

The combined vaccine efficacy in rounds 13 and 14 for all participants and all vaccines from 18-64 years proved to be 63% after full vaccination, compared to the unvaccinated. When analyzed by vaccine, the efficacy was 45% for the AstraZeneca vaccine but 71% for the Pfizer/BioNTech vaccine.

The combined vaccine efficacy against symptomatic infection was 66% overall. The prevalence of positive swab tests was 1.8% among the unvaccinated. In contrast, it was 0.55% among those aged 18 years or more who had been fully vaccinated 3-6 months before the test, and 0.35% among those who had received the second dose within three months of the swab.

Unvaccinated people had a prevalence of 2.3% vs. 0.55% among the fully vaccinated.

What are the implications?

The exponential rise in infections among those aged 5-17 years occurred simultaneously as the reopening of schools in England for the fall term. The low vaccine coverage in this age group may be responsible for this, though at present, children of 12 or above are being offered one dose. Vaccination reduces swab positivity by three to four times compared to those who have received two doses, though the immunity appears to wane after three to six months.

Vaccination has proved to be very effective against severe COVID-19 but may also prevent infections by up to 90%.

Following the vaccination campaign there has been a relative uncoupling between infections and hospitalizations and deaths in England,” say the researchers.

However, the relevance of a third booster dose is supported by the increased swab positivity rate among those who had the second dose 3-6 months earlier, compared to those who were fully vaccinated three months before. Continuing monitoring will allow a better evaluation of the impact of the booster doses in adults and pediatric vaccination on the spread of the virus.

Though swab positivity rose exponentially among children, it fell among adults 18-54 years, probably the effect of high immunity due to both natural infection and high vaccination coverage. Vaccine-dependent variations in efficacy involve not just the type of the vaccine, though that is important, but also the age group to which each was primarily administered and the level of restrictions at the time of vaccination.

As the flu season begins, the researchers conclude,

It is important that the vaccination programme maintains high coverage and reaches children and unvaccinated or partially vaccinated adults to reduce transmission and associated disruptions to work and education.”

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

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