Challenging Vaccination with 1st and 2nd Generation Smallpox Vaccines... "Urgent Need to Introduce 3rd Generation"

[Image source=Reuters Yonhap News]

[Asia Economy Reporter Kim Young-won] As the first confirmed case of monkeypox was reported in South Korea, attention is also focusing on monkeypox vaccines.

Currently, South Korea has stockpiled 35.02 million doses of 1st and 2nd generation (human) smallpox vaccines to prepare for bioterrorism or national public health crises. However, since these old smallpox vaccines are difficult to administer and may cause adverse reactions, there is a view that the introduction of 3rd generation monkeypox vaccines should be accelerated. The government is in talks with manufacturers to introduce 3rd generation vaccines.

According to the Ministry of Food and Drug Safety and the pharmaceutical industry, as of the 24th, the only smallpox vaccine approved in South Korea is HK Innoen's "Innoen Cell Culture Dry Smallpox Vaccine." It is a live attenuated vaccine that weakens the toxicity of the live virus and was approved by the Ministry of Food and Drug Safety on December 31, 2008. Since smallpox vaccination was discontinued in 1979, this product was developed for bioterrorism response. Although its effectiveness in preventing monkeypox has not been officially recognized, authorities state that human smallpox vaccines have about 85% preventive efficacy against monkeypox.

However, the vaccination method is complicated, and it is considered a limitation that adverse reactions are more likely to occur compared to 3rd generation vaccines. This vaccine is not administered by injection but by dipping a bifurcated needle into the vaccine vial and pressing it vertically into the skin 15 times until blood appears. After vaccination, a skin immune response such as pustules appears at the injection site; this reaction indicates successful vaccination but must be carefully managed by not touching it until it naturally falls off.

Most adverse reactions are mild pain at the injection site, but severe adverse reactions can worsen to high fever, eczema, myocarditis, encephalitis, and other conditions.

On the other hand, 3rd generation smallpox vaccines are known to be safer than older vaccines. A report published by the Korea Disease Control and Prevention Agency in December last year stated, "So far, 3rd generation smallpox vaccines are known to be the most effective vaccines in terms of safety." The vaccine "Jynneos," developed by Denmark's Bavarian Nordic, is a representative 3rd generation smallpox vaccine. It was also approved in the United States in 2019 for monkeypox prevention. The 3rd generation vaccine can be administered by common methods such as subcutaneous injection.

Experts recommend introducing the 3rd generation vaccine, which is safer and easier to administer. Professor Lee Jae-gap of the Department of Infectious Diseases at Hallym University Kangnam Sacred Heart Hospital said, "The domestic vaccine is approved for smallpox, not monkeypox, and although adverse reactions have decreased compared to the 1st generation, there is still a possibility of adverse reactions and the vaccination method is complicated. Currently, monkeypox is not widespread enough to require vaccinating the entire population, so it is sufficient to obtain and use the 3rd generation vaccine."

The government is also considering vaccinating only high-risk groups exposed to infection rather than the general public, considering the low transmissibility of monkeypox.

Meanwhile, HK Innoen is consulting with the Ministry of Food and Drug Safety and the Korea Disease Control and Prevention Agency regarding clinical trials to confirm the monkeypox preventive effect of its smallpox vaccine. HK Innoen is also developing a 3rd generation smallpox vaccine, but it is known to still be in the preclinical stage.