As Japan faces yet another wave of COVID-19 infections ahead of the New Year's holiday season, there's been a shortage of traditional Chinese kanpō medicine that doctors sometimes prescribe to patients.

A recent study in Japan that examined the effects of kanpō on COVID-19 symptoms may further heighten their demand. The research, conducted by Tohoku University and published in November, led some domestic media to report its positive findings. But a closer look at the results shows that its effectiveness appears to be limited.

Earlier this month, Tsumura, which supplies over 80% of all prescription kanpō medicine in Japan, released a statement to doctors explaining that, since August, their supply has not been stable due to “demand that far exceeded expectations for products related to COVID-19 and seasonal (illnesses).”

“We have boosted production on some of our products to address concerns about stable supply,” Tsumura said in the statement. “That led to the easing of supply on two products in October and three more in November. But we will still need to restrict our shipments (of 23 items).”

Tsumura's latest statement follows one released at the height of the nation’s largest and deadliest seventh COVID-19 wave, saying 28 items were in short supply.

Kanpō medicine is widely used at Japanese clinics and hospitals, where doctors trained in Western medicine write prescriptions for it depending on the patients’ symptoms, which could range from a stuffy nose, throat pain or cough. Kanpō, based on ancient Chinese herbal medicine and administered in granule form, is covered by the public health insurance program.

Kanpō is also widely available at pharmacies over the counter, with manufacturers such as Kracie and Kotaro offering a range of products in granules and syrups, to respond to everything from stomach pain and constipation to insomnia and hay fever.

Furthermore, bags containing medicinal herbs for decoction and subsequent consumption — a method common in China and across Asia — can be purchased from kanpō pharmacies (called kanpō yakkyoku in Japanese). Such medicines, along with other over-the-counter products, are not covered by public health insurance.

The widespread use and availability of kanpō in Japan, as opposed to other oral medicines recently approved for COVID-19, has given some people hope that it may work as a viable treatment for the viral disease. The scientific evidence so far, however, remains weak.

In the latest Tohoku University study, which targeted patients with mild to moderate COVID-19, participants were randomly assigned to two groups. The first group of 81 people were given two types of kanpō formulas in addition to conventional fever and cough relievers, while the second 80-member group was given the conventional medicine only. Both groups took the medicine three times a day for 14 days.

The two kanpō formulas were kakkontō — which contains kudzu root — often used to relieve early cold symptoms such as headache and fever, and shō-saiko-tō-ka-kikyō-sekkō — which contains a mix of herbs including mineral gypsum and bupleurum roots — used to relieve throat pain and swelling.

The researchers wrote that there was “no significant difference” in symptom relief between the two groups on “primary outcomes” of the study – its most important part. But they also wrote that some effects were observed in those who were given kanpō, such as fever going down faster, after factors such as age, severity and vaccination status of the patients were statistically adjusted.

A news release about the study, with the headline, “fever relief and the suppression of the disease progressing to severe symptoms were confirmed through the administration of kanpō,” has been making the rounds on social media, along with other media reports touting its positive effects.

Shin Takayama, a specially appointed professor at Tohoku University and the first author of the paper, said in an email that the results of the trial were “mixed.”

“Through statistical analysis, shorter fever duration days and lower risks of the conditions leading to respiratory failure were seen, which were summarized (in the news release’s title and main research points),” Takayama said.