The SARS-CoV-2 Alpha (B117) variant spread faster and more efficiently than previous strains among children 9 years and younger in Israel in late 2020 and early 2021, even amid the concurrent immunization of adults against COVID-19, according to an observational study yesterday in JAMA Network Open.
A team led by a researcher at Schneider Children's Medical Center of Israel in Petah Tikva compared the publicly available daily data of 21,615 children who tested positive for COVID-19 from Aug 1 to Oct 2, 2020, with those of 50,811 children who tested positive from Dec 3, 2020, to Feb 3, 2021. The researchers adjusted weekly incidence rates according to the number of COVID-19 tests performed.
Similar scenario in adults
Coronavirus transmission rates doubled—but hospitalization rates dropped—after Alpha emerged in December 2020 and quickly unseated earlier strains as the dominant virus. The same scenario occurred in adults, with increased contagiousness but not severity. As Israel rolled out COVID-19 vaccines to adults, Alpha came to account for 80% of cases.
The slopes of weekly adjusted incidence curves for children younger than 9 years were significantly higher in December to February than those in August to October (84.4 vs 39.1). The rate ratio (RR) of highest to lowest weekly incidence was also higher in the latter period (6.75 vs 3.62).
From December 2020 to April 2021, 15.7% of secondary cases identified through contact tracing involved children 9 years and younger (RR, 2.24), compared with 7.5% from February to November 2020.
A total of 0.98% of children who tested positive for COVID-19 from August to October 2020 were hospitalized, compared with 0.52% during December to February 2021 (RR, 0.53). However, the percentage of hospitalized children who became severely ill or died was similar in both periods (6.5% in the earlier period and 6.9% in the latter; RR, 0.99).
A call to authorize vaccines for young kids
Israel went into lockdown twice over the study period, from Sep 18 to Oct 13, 2020, and from Jan 8 to Feb 7, 2021. Schools closed from Sept 14 to Nov 1, 2020, and from Jan 8 to Feb 15, 2021. The country's COVID-19 immunization effort began on Dec 20, 2020, vaccinating 57% of adults with the first dose of the Pfizer/BioNTech vaccine by Feb 3, 2021.
The researchers noted that the rapid spread of Alpha despite the expected mitigating effect of mass vaccination of adults in Israel underscores the importance of making COVID-19 vaccine available for young children. "Nonpharmacologic measures such as lockdown and school closure could not account for the difference in transmission since they were used during both periods," they wrote.
While the authors acknowledged that factors other than Alpha may have contributed to the rapid coronavirus spread, they urged action to protect children. "These findings suggest that health authorities in different regions should anticipate this occurrence and implement measures to reduce spread in young children both in schools and at home," they wrote.