Photo/Illutration Children receive a shot of vaccine against the coronavirus at Aiiku Hospital in Tokyo’s Minato Ward on March 1. (Shinnosuke Ito)

The number of children and teens under 20 who have contracted the coronavirus topped 1.04 million across Japan as of Feb. 22, and most of those cases were relatively recent.

More than 70 percent caught the virus during the current sixth wave of infections fueled by the Omicron variant, according to the health ministry.

Infections spiked sharply for children under age 10 in recent weeks--the age group that has yet to be vaccinated, the ministry added.

As of Feb. 22, about 320,000 children in this age bracket were infected with the coronavirus over the preceding four weeks, accounting for 15 percent of the total caseload.

But most developed only mild symptoms or none at all, the Ministry of Health, Labor and Welfare said.

So far, no COVID-19-related deaths have been reported for children aged 9 or younger who became infected.

However, six teenagers have died, the ministry reported.

About a dozen or so children under 10 were diagnosed with multisystem inflammatory syndrome as an aftereffect from contracting COVID-19.

This month, Japan began inoculating children between ages 5 to 11 with two Pfizer shots administered with a three-week interval between them.

Overseas clinical trials of children aged 5 to 11 showed that arm pain is the most common side effect after getting the shot, at 71 percent. It was followed by fatigue at 39.4 percent, headaches at 28 percent and a fever of 38 degrees or higher at 6.5 percent.

This age group had fewer of these side effects than those in children 12 or older, the data showed.

The results of the clinical trials also found that two doses of the Pfizer vaccine were 90.7 percent effective in preventing children 5 to 11 from developing symptoms.

But the findings were drawn from the time when Delta was raging around the world, not after the surge of Omicron.

A recent U.S. study, which has yet to be peer reviewed but was carried by The New York Times on Feb. 28, reported that the Pfizer vaccine is much less effective in preventing infections in children ages 5 to 11, compared with those 12 to 17.

The study analyzed data on fully vaccinated children in the state of New York.

Vaccine effectiveness against infection in children 12 to 17 dropped to 51 percent in late January from 66 percent in the middle of December.

For children 5 to 11, it was down to 12 percent from 68 percent.

The report said one reason for the steep drop could be that the younger children received only one-third the dose given to older children.

On March 1, Japan reported 65,434 new cases of COVID-19 nationwide, 4,078 fewer than the previous Tuesday.

The latest daily count included 11,813 new cases in Tokyo and 8,966 new cases in Osaka Prefecture.

The number of serious cases, such as patients in ICUs, totaled 1,456 as of Feb. 28 across the country, down five from the day before.

There were 238 related deaths on March 1.

(This article was written by Hiromi Kumai and Roku Goda.)

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