SK bioscience restarts flu shot production after 2 years

The flu season is back in full swing, and so is SK bioscience’s production of Korea’s first and only cell-based influenza vaccine.

Pre-filled syringes of SKYCellflu influenza vaccine on the packaging line at SK bioscience’s Andong L House manufacturing plant in North Gyeongsang on Tuesday [SHIN HA-NEE]

ANDONG, North Gyeongsang — As Covid-19 becomes endemic, the flu season is back in full swing, and so is SK bioscience’s production of Korea’s first and only cell-based influenza vaccine.

SK bioscience is making a comeback in the domestic flu shot market after a two-year hiatus, during which the company focused on producing its Covid-19 vaccine SKYCovione.

Now, with flu cases surging across the country in a rare occurrence and the crisis level for Covid-19 set to be further downgraded, things are up and running again on the production lines for SK bioscience’s SKYCellflu, a cell-based quadrivalent influenza vaccine.

Pre-filled syringes of SKYCellflu influenza vaccine on the packaging line at SK bioscience’s Andong L House manufacturing plant in North Gyeongsang on Tuesday [SHIN HA-NEE]

“While flu season is usually [from November] until April, this season’s influenza activity is still there even in the summer,” Kim Gi-hyeon, head of the medical information team at SK bioscience, told the press on Tuesday at the Andong L House, the company’s vaccine manufacturing center in North Gyeongsang.

“Considering this trend, we expect the burden of the disease will continuously grow,” Kim added.

The unusual trend for the late spring and summer outbreak is likely due to the removal of the indoor mask mandate. Herd immunity against influenza viruses, usually built during the winter at the peak of flu season, was not sufficiently established this year due to the mask mandate, resulting in weaker immunity against the seasonal flu.

When journalists visited the Andong L House on Tuesday, millions of doses of influenza vaccines were being readied for shipment.

Five-milliliter syringes filled with SKYCelllflu were waiting on the production line as machines busily ran automated quality checks and packed syringes in boxes. Package after package was being stacked, while employees in clean room garments moved the boxes, each filled with 150,000 doses of flu shots, to prepare them for shipping.

SK bioscience's SKYCellflu influenza vaccine [SK BIOSCIENCE]

Starting Wednesday, SK bioscience will supply some 5 million doses of SKYCellflu vaccines across the country until October.

SKYCellflu, launched in 2016, was granted the World Health Organization's first-ever pre-qualification certification for a cell-cultured quadrivalent influenza vaccine in 2019. It is currently the only cell-based vaccine available in Korea.

There are two types of technologies for producing influenza vaccines: Egg-based and cell-based.

Traditional egg-based flu vaccines, which take up a majority of the market, are made with fertilized chicken eggs by injecting candidate vaccine viruses before harvesting virus antigens from the egg. Meanwhile, cell-based vaccines are made with cultured animal cells.

The cell-based technology could possibly improve the vaccine's effectiveness, as growing influenza viruses in eggs may cause egg-adapted changes that result in a difference between the virus in the vaccine products and the actual flu virus circulating during the season.

As such, Britain’s Joint Committee on Vaccination and Immunisation suggested in a statement on influenza vaccines for the 2023/24 season that “there is a potential advantage to using influenza vaccines which do not use eggs in the manufacturing process [cell-culture or recombinant] compared with egg-cultured influenza vaccines, due to the possible impact of ‘egg-adaptation’ on the effectiveness of influenza vaccines.”

An employee with a syringe of SK bioscience's SKYCellflu influenza vaccine[SK BIOSCIENCE]

Moreover, cell-based vaccines are safe for people with egg allergies, and as the production of cell-based vaccines is not dependent on egg supply, aligning production with demand is easier for cell culture vaccines.

“Egg-based vaccines are usually referred to as more classic ones, whereas cell-based vaccines are often dubbed the next-generation,” said Lee Sang-gyun, SK bioscience senior vice president and chief of the Andong L House.

SK’s SKYCellflu is priced almost on par with the traditional egg-based flu shots in the market, Lee added.

SKYCellflu is the leading flu shot market in Korea and received approval from 10 countries including Malaysia, Thailand, Singapore and Mongolia.

The Andong L House measures 62,626 square meters (15.5 acres), with a 99,130-square-meter site expansion underway. The plant can produce up to 500 million vaccine doses annually.

BY SHIN HA-NEE [shin.hanee@joongang.co.kr]