Japan's health ministry reported Wednesday a further eight incidents of people experiencing severe allergic reactions after receiving a COVID-19 jab, with the minister in charge of vaccination efforts saying such occurrences were high in Japan.
The ministry also said separately that concerns were mounting over increasing number of people testing positive for variants of the novel coronavirus, thought to be particularly contagious.
The minister in charge of vaccination efforts, Taro Kono, said Wednesday that incidents of anaphylaxis after receiving the coronavirus vaccines developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech SE, were higher in Japan than in the United States and Europe.
The total cases of anaphylaxis among health care workers being inoculated here has now risen to 25 from 17 reported earlier, the health ministry said.
Anaphylaxis is a potentially lethal and acute allergic reaction to an antigen to which the body has become hypersensitive.
"It's true, this seems to be more than in the United States and Europe," Kono told a parliamentary committee after detailing the cases of anaphylaxis reported among around 148,000 health care workers who had been inoculated as of Wednesday.
By comparison, five cases of anaphylaxis in every 1 million doses given in the United States have been reported and 20 cases per 1 million in Britain.
Japan's public broadcaster NHK earlier in the day said the ratio of those going into anaphylactic shock after receiving the Pfizer jab in Japan was about 1 in 6,300 people, although the ratio has since increased owing to the additional eight cases since reported Wednesday.
According to the health ministry, medical facilities reported that female medical workers aged in their 20s to 50s were the ones to predominantly experience anaphylaxis after receiving the Pfizer jab, although the first male case has now also been reported.
The symptoms of anaphylaxis include, but are not limited to, coughing, wheezing, tightness in the chest, general pain, trouble breathing, rapid heartbeat, swollen or itchy throat, tightness in the throat, vomiting, diarrhea and a weak pulse, health experts here said.
They added that when someone goes into potentially life-threatening anaphylactic shock, which among the symptoms will almost certainly include their blood pressure suddenly dropping, a narrowing of their airways, and the blocking of normal breathing, they need immediate emergency medical attention.
If the reaction is not treated immediately, it can result in serious complications and can be fatal, they said.
In addition, according to the experts, one out of every five people may have a second anaphylactic reaction within 12 hours of the first, known as biphasic anaphylaxis.
The health ministry said those who experienced anaphylaxis after the Pfizer jab was administered, despite displaying severe reactions, have all since recovered.
An investigation led by a panel of experts at the health ministry has been charged with investigating the link between the Pfizer vaccine and the anaphylactic shock.
Japan's health minister Norihisa Tamura said a ministry panel will look into the issue on Friday and try to determine whether the symptoms in Japan were as serious as those overseas.
Meanwhile, Japan's health ministry on Wednesday said separately that the number of people testing positive for variants of the novel coronavirus first detected in Britain, Brazil and South Africa had reached 345.
The Japanese government has expressed its concern over the spread of the COVID-19 virus variants, known to be more transmissible than the original virus, amid uncertainty whether the vaccines it has procured will be effective against the variants.
The head of the government's COVID-19 subcommittee, Shigeru Omi, at a parliamentary committee session on Wednesday warned that variants would "become the dominant strain in Japan sooner or later."
Health officials have said that the majority of people infected with the variants in Japan have tested positive for the variant first found in Britain.
The variants first found in Brazil and South Africa, however, are thought to be more highly contagious, virologists with knowledge of the matter have attested.
As the vaccine rollout campaign continues to expand nationwide in Japan, the government is ramping up efforts to conduct more polymerase chain reaction (PCR) tests in a bid to detect virus variants.