"COVID-19 can lead to 'long COVID,' and its progression tends to be more severe among the elderly and immunocompromised individuals. It is crucial to emphasize COVID-19 prevention as the saying goes, 'an ounce of prevention is worth a pound of cure.'

After the announcement of the endemic in 2023, COVID-19 has repeatedly mutated, thus regarded as becoming a 'resident virus' that makes a comeback similar to influenza.

Although determining the exact seasonal pattern of COVID-19 may require more time, the government provides vaccination to high-risk groups, such as individuals aged 65 and older.

During a meeting with Daily Pharm, Dr. Woo Joo Kim, a professor in the Department of Infectious Diseases at Korea University Guro Hospital, emphasized the importance of reducing the disease burden by putting efforts into increasing the COVID-19 vaccination rate.

Currently, the legal status of COVID-19 has been designated as a class 4 infectious disease in South Korea after the endemic announcement in 2023. Like influenza, COVID-19 is categorized as an infectious disease requiring daily monitoring.

Despite the initial expectation that COVID-19 will show seasonal spikes, it has not demonstrated a clear seasonal pattern like influenza.

Dr. Kim explained, "COVID-19 is likely in a 'transition period.' The severity is lowered compared to the earlier phase of the pandemic due to vaccination, but it is yet to be defined as a seasonal virus," adding, "In the past few years, COVID-19 made a comeback in around January-February and around August. However, it is yet too soon to generalize."

"Over the past four years, the severity of COVID-19 has diminished compared to its early phase, thanks to immunity acquired through vaccination and natural infection. However, high-risk groups, including the elderly, individuals with underlying conditions, immunocompromised patients, pregnant women, and residents of long-term care facilities, continue to face a significant burden of disease, with a high risk of severe illness or death," Dr. Kim said.

Dr. Kim's attention to the COVID-19 vaccine during this transitional period is because COVID-19 exhibits infection characteristics distinct from those of influenza.

While both diseases may be perceived as similar, there are clear differences in infection patterns, causative pathogens, and complications. The influenza virus causes influenza, whereas COVID-19 is caused by SARS-CoV-2.

"The COVID-19 virus not only targets the respiratory system but also invades the vascular system, kidneys, and other organs, causing a systemic infection with higher severity and fatality rates," Dr. Kim stated. "Long COVID, affecting the entire body as a sequela, can occur, and its impact tends to be more severe in older individuals or those with weakened immune systems."

Although COVID-19 and influenza share similar symptoms and some complications, which can lead to them being conflated, experts warn that this may result in the risks of COVID-19 being underestimated, calling for heightened vigilance."

For these reasons, the government is currently administering COVID-19 vaccines to high-risk groups, including individuals aged 65 and older, immunocompromised persons aged at least 6 months, and residents of facilities vulnerable to infections, to prevent severe illness and death.

The ongoing issue is whether to include the COVID-19 vaccine in the National Immunization Program (NIP). There is a growing consensus that incorporating the COVID-19 vaccine into the NIP is essential to boost vaccination rates for the currently administered vaccines."

Dr. Kim said, "In addition to preventing infections, hospitalizations, and deaths at the individual level, incorporating the COVID-19 vaccine into the NIP is essential for sustaining our national population. For instance, by systematically benchmarking the well-established NIP for the influenza vaccine in individuals 65 and older, we can effectively plan and implement a similar strategy for the COVID-19 vaccine."

There is ongoing concern about determining the optimal vaccination schedule, as it remains difficult to predict the precise timing of the COVID-19 surge.

Dr. Kim emphasized, "When establishing the vaccination schedule for the COVID-19 vaccine, it is crucial to base decisions on scientific evidence regarding the outbreak period, the duration of antibody persistence, and the vaccine's ability to counter emerging variants." He advised, "Antibodies may not form adequately or may quickly be depleted in individuals with severe immunocompromise. It is advisable to tailor the dosing frequency and timing based on each patient's immune status."

Dr. Kim added, "High-risk groups such as immunocompromised individuals and residents of long-term care facilities face a significantly higher risk of severe illness if infected, yet their vaccination rates remain low. If we were to improve COVID-19 vaccination rates, government's promotional activities is essential."

"COVID-10 vaccination can be compared to wearing a seat belt, lowering severity"

Currently, two mRNA COVID-19 vaccines are available in Korea. Aside from a minor difference in antigen dosage (approximately 30 to 50 micrograms) their basic compositions, including encapsulation in lipid nanoparticles, are virtually identical.

In clinical practice, healthcare providers typically use whichever vaccine is distributed to their institutions and available for immediate use.

However, due to differences in domestically imported volumes, over 80% of vaccinations administered during 2023–2024 were Pfizer's Comirnaty.

In global Phase 3 trials, Comirnaty demonstrated a 95% preventive efficacy across COVID-19–naïve and previously infected participants, with overall safety profiles remaining favorable.

Dr. Kim explained, "mRNA vaccines like Comirnaty induce a robust T-cell immune response, ensuring that the benefits of preventing severe disease and death are sustained over a long period. The Korea Disease Control and Prevention Agency also strongly emphasizes these outcomes when recommending COVID-19 vaccination."

One of the concerns raised about COVID-19 vaccines has been safety issues that emerged during the pandemic. However, Dr. Kim believes that confidence in the vaccine's safety has increased.

He noted, "Among high-risk groups such as those aged 65 and older or individuals with underlying conditions, no significant adverse reactions have been observed, and the benefits of vaccination are substantially greater," adding, "With sufficient vaccination experience now accumulated and those who experienced adverse reactions subsequently excluded from further dosing, the incidence of adverse events in recent vaccination cohorts is very low."

He particularly compared vaccination to wearing a 'seat belt.' Although wearing a seat belt can be uncomfortable and does not guarantee 100% prevention of injuries, it significantly reduces the risk when an accident occurs. Similarly, COVID-19 vaccination is essential to lower the risks of infection and severe disease.

Lastly, Dr. Kim stressed that a coordinated effort at the individual, societal, and government levels remains critical for effective COVID-19 management.

Dr. Kim said, "High-risk groups, such as the elderly and those with underlying conditions, must recognize their risk of infection and proactively get vaccinated, and if they experience symptoms, they should promptly seek diagnosis and treatment," adding, "I believe including the COVID-19 vaccine in the NIP can be expedited if individuals actively voice their concerns."

"On a societal level, we need to foster a 'take a break when you're sick' culture, and at the government level, it is essential to establish an independent monitoring system solely for COVID-19," Dr. Kim added. "The government must quickly set vaccination schedules and develop promotional strategies based on up-to-date data on the latest COVID-19 outbreak patterns, disease burden, and the efficacy and safety of vaccines."