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Experts move to allay replicon COVID shot fears in Japan amid backlash

Sulaiman Umar
07 Oct, 2024
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A new COVID-19 vaccine has sparked extreme anxiety among parts of the public, leading some businesses to deny services to those who have received the shot and causing at least one clinic to stop giving the vaccine for fear of being harassed.

The health ministry and experts say such fears — fueled by comments circulated both online and offline that the vaccine multiplies in the body indefinitely and as a result causes the “shedding” of its ingredients from an inoculated person to unvaccinated individuals — are unwarranted.

“There’s no scientific evidence that the replicon vaccine will make an infinite number of proteins in the body or its components will be transmitted to others,” the health ministry states on its website.

One of the five shots included in the government’s routine COVID-19 vaccination program, which began Oct. 1 and runs until the end of March, is the replicon vaccine Kostaive. Once inside the body, it uses a self-amplifying messenger RNA that creates proteins evoking immune responses against the coronavirus.

U.S.-based Arcturus Therapeutics developed Kostaive to address the shortcomings of earlier mRNA vaccines, which can only keep infection or the development of symptoms at bay for a few months.

The vaccine can evoke a stronger and more sustained immune response using a smaller dose than conventional mRNA vaccines, according to Meiji Seika Pharma, which manufactures and markets the shot in Japan.

In the last stage of a clinical trial using the vaccine as the initial shot, which was conducted in Vietnam during a delta variant wave and involving 16,000 people, Kostaive was shown to prevent the development of severe illness in 95.3% of those who received it while preventing symptoms from emerging in 56.6% of recipients.

In a separate trial for a booster shot comparing Kostaive and Pfizer’s Cominarty shot involving 828 people in Japan, the former was shown to sustain higher levels of antibodies, with comparable levels of side effects that were either minor or mild, according to data provided to the health ministry.

Japan was the first country to approve this “next-generation” mRNA vaccine, while the European Medicines Agency is currently reviewing Arcturus’ request for the vaccine’s approval in the European Union.

In Japan, fears about the vaccine’s safety have spiraled. In August, the Japan Nursing Ethics Association, a group of nursing ethics researchers, released a statement questioning the vaccine’s safety. The statement referred to the danger of vaccine shedding from the inoculated to the unvaccinated, quoting a paper published in a U.S. journal largely known for its opposition to vaccines.

The panic over shedding escalated last week, when the major yoga chain Lava announced an entry ban for those who have received this replicon vaccine “until its safety is confirmed.” Lava runs over 500 yoga studios across Japan.

One clinic in Tokyo’s Kita Ward even suspended reservations for the vaccine after it was inundated with threats and harassment from those protesting against the replicon vaccine.

“It has become difficult to respond to reservation inquiries about the world's first replicon vaccine,” the clinic, run by Dr. Hiromichi Ito, wrote on its website. “While we believe that the theoretical and scientific data (on the vaccine’s safety) are acceptable, the public opposition has been so extreme. We have received threats and slander on social media and harassing phone calls even late at night.”

Yuji Yamada, assistant professor of geriatrics at the Icahn School of Medicine at Mount Sinai in New York, called the nursing ethics association’s statement “pretty horrible,” saying it was given a false sense of authority by quoting a paper that may look reputable to some but which is scientifically flawed.

“The statement cites a paper in which the authors imagine that shedding could occur with this vaccine and say that there is concern about shedding, but in reality, there is no paper that has proven shedding at all.”

The word “shedding” is often used to refer to the transmission of a virus to humans through saliva or droplets after the virus replicates in the body. Yamada says there is no possibility of Kostaive causing the virus to be transmitted.

“This vaccine only contains mRNA that produces spike proteins, so it is impossible to create a complete virus,” he said.

In addition, mRNA easily breaks down in cells, so even if the vaccine’s mRNA lasts longer than other mRNA shots, it won’t keep multiplying forever, he said. Meiji Seika Pharma says the amplification period is short, noting that animal studies have shown significantly fewer mRNA at the injection site eight days after inoculation.

But some doctors have, for now, stopped short of actively recommending the replicon vaccine, given the abundance of other mRNA vaccines that have been used around the world and whose safety has been well established.

Yamada added that, in general, the use of the self-amplifying vaccine is not advisable for people taking immunosuppressants and pregnant women, as clinical studies have so far excluded them.

“It’s just that the data (involving these groups of people) aren’t fully there yet for the vaccine, so I would recommend other options,” he said.

Setting aside safety concerns, Kostaive won’t probably be widely available this year anyway, Yamada said, noting that small clinics administering COVID-19 shots are shying away from stocking the vaccine for financial reasons.

As one vial of Kostaive contains 16 doses, some clinics are worried about the prospect of not using up all the doses within one month, the period during which an unsealed vial can be kept, he said. If they do not use up their doses, the clinics could lose money.

Until April 2023, COVID-19 vaccinations were classified as temporary inoculations and offered for free, with the central government paying the full cost. From April 2025, COVID-19 shots will be administered as part of an annual routine inoculation program similar to seasonal flu shots.

COVID-19 shots are recommended for people age 65 or older and those between the ages of 60 and 64 with severe underlying conditions. The health ministry subsidizes the shots to cap out-of-pocket expenses at ¥7,000 ($47), and some municipalities offer subsidies to bring the fee down or offer them for free.

culled from Japan Times