• CORONAVIRUS

New vaccine expected to boost omicron protection for all generations

Yomiuri Shimbun file photo
A person receives her fourth dose, now available to those aged 60 or over and to people with preexisting medical conditions, at a vaccination site in Minato Ward, Tokyo. (This photo was taken in May.)

The Health, Labor and Welfare Ministry plans to start administering COVID boosters using a new vaccine that is expected to increase protection against the omicron variants, as early as mid-October.

The new vaccine is expected to be administered to people of all ages who have received their second vaccination. The goal is to balance curbing the spread of infections with maintaining social and economic activities.

On the other hand, it is feared that some people might shy away from getting their fourth dose — now available for people age 60 or over and those with preexisting medical conditions — and wait for the new vaccine instead.

‘Bivalent vaccine’

“We can expect that [a new vaccine] will not only prevent patients from becoming seriously ill but will also prevent people from getting infected and experiencing the onset of the infectious disease.”

At a subcommittee of an expert meeting of the health ministry, held on Aug. 8, positive opinions in favor of using the new vaccine were voiced one after another.

The new vaccine is a type of “bivalent vaccine,” which combines components of the current vaccine that responds to the strain known as Wuhan-Hu-1, with elements that respond to the omicron subvariant BA.1, the first omicron subvariant.

The World Health Organization (WHO), for its part, is of the opinion that the new vaccine “could be beneficial.”

U.S. biotechnology firms Pfizer Inc. and Moderna, Inc. applied on Aug. 8 and 10, respectively, for approval from the health ministry to use their new vaccines. Both firms said they will be able to import their products into Japan within September.

Both firms have been developing new vaccines that would elicit better responses against the omicron subvariant BA.5, which is currently the dominant variant. But the health ministry preferred to switch to the vaccine that is most readily available. The new vaccine is also considered to generate certain effects against the BA.5 variant.

Antibody response

The omicron strain has a lower risk of causing serious illness, but can evade previously acquired immunity and is thus highly infectious. By having repeatedly mutated from previous strains, there have been about 30 mutations of its spike proteins, which form spike-like structures on the surface of the virus and are involved in infection. This makes the current vaccine less effective.

The seventh wave has impacted not only the occupancy rate of hospital beds but also the social infrastructure, as seen in reduced train and bus services. In light of these developments, new steps that can cope with powerful viruses are called for.

It is assumed the new vaccine will be given to people of all ages, rather than only to elderly people who have a higher risk of falling seriously ill, as it is aimed at not only protecting individuals but also at raising the proportion of those who have immunity in society as a whole.

The new vaccine has been proven to generate a stronger neutralizing antibody response — which prevents infection — against omicron than the current vaccine by a factor of 1.56 to 1.97. Francesca Ceddia, senior vice president at Moderna, said that with the use of the combined elements of the two strains, the immunological strength is believed to have been enhanced.

Challenges ahead

While expectations grow for the new vaccine, many challenges lie ahead.

As data has been produced on only its neutralizing antibody response against omicron, it remains unclear how effective it is in preventing people from getting infected or blocking the onset of COVID-19, when compared with the current vaccine.

More worrisome is the possibility of people holding back from getting a booster of the current vaccine.

For instance, if an elderly person gets his or her fourth shot with the current vaccine this month, they cannot get a dose of the new vaccine until later than next January, a five-month interval. But if they do not get a fourth shot with the current vaccine anytime soon, they may be able to get the new vaccine as early as mid-October.

Yet, an expert warns, “If they delay their fourth shot, their immunity will fall in the meantime.”

Atsuo Hamada, a specially appointed professor at Tokyo Medical University who specializes in infectious diseases, said: “As the current vaccine is also effective in preventing infected people from becoming seriously ill, we want them to receive an additional shot when the time comes.

“The central government should make sufficient announcements concerning the vaccine so that people do not shy away from getting an additional dose.”

There are also concerns that a new variant other than omicron could prevail in the future.

Tetsuo Nakayama, a specially appointed professor at Kitasato University who specializes in clinical virology, said: “We cannot return to our peaceful social life with the new vaccine alone.

“New measures must be worked out in step with the emergence of new variants in the future, as well.”