The Covid-19 pandemic has been resurging since last month. As the number of confirmed cases increased sharply, the planned easing of social distancing has been shelved. Moreover, the Delta variant has become the most dominant strain in Korea (Fig. 1).

However, unlike the past three viral waves, the numbers of deaths and critically ill patients have not sharply increased despite the rapid spread of the Delta variant in the ongoing fourth wave. (Fig. 2). Such a phenomenon has been observed in most countries with high vaccination rates, providing a new perspective on Covid-19.

Coexistence with Covid-19 has been proposed in the United Kingdom and Singapore, but their strategies differ significantly. The U.K. declared Freedom Day on July 19 and lifted most lockdown restrictions. Singapore has proposed a gradual easing of lockdown measures while treating Covid-19 as an endemic, but the schedule has been delayed due to the resurgence of the Delta variant.

We have accumulated considerable knowledge on Covid-19. First, there is an apparent high-risk group for Covid-19. The mortality rate changes rapidly with age and underlying disease. Therefore, the use of vaccines to protect high-risk groups can minimize damage. 

Second, the variants of concern have emerged, and the effectiveness of vaccines to prevent infection is gradually decreasing. However, the clinical effect of preventing severe cases and deaths is stably maintained at a high level. 

Third, non-pharmaceutical interventions, such as social distancing, lockdown, epidemiological investigations, and diagnostic tests have been effective but challenging to maintain because of the substantial socio-economic losses. 

Lastly, the basic reproduction number of the delta variant has risen to a level where it is difficult to form herd immunity with vaccination-only.

Therefore, Covid-19 will not easily disappear. It will survive and threaten us for several generations. It can be temporarily controlled, but multiple variants will persistently emerge and periodically infiltrate into Korea. Even if the 70 percent level of herd immunity suggested by the government is reached, it will be difficult to control the pandemic completely. The pandemic will not end clearly like the end of a war; it will just slowly become considered insignificant.

No solution will satisfy everyone. The side effects of preventive measures have affected the self-employed and small businesses, and ensuring society's safety can be a serious threat to some people's survival. With the delayed social distancing reorganization plan, many people have become impatient. Preventive measures can and should become flexible depending on the situation. There is no ideal end to the pandemic. Therefore, social consensus on the timing and plan for its future is necessary.

Experts consider that the pandemic will begin to end once high-risk groups are entirely protected. Furthermore, clear definitions of high-risk groups and the completion of protection are needed. For example, people aged 50 years or older can be the standard high-risk group. If a large outbreak affects them, critically ill patients will increase, possibly becoming a social risk. 
It is necessary to protect this group as they are socially active, have a high risk of infection, and have fatality and high severity rates of 0.3 percent and 1.5 percent, respectively. 

Even people under 50 years should be protected if they have underlying diseases, such as diabetes and chronic kidney disease. Considering the vaccine efficacy in Korea and the prevalence of the delta variant, it is difficult to regard single-dose vaccination as “complete protection.” It is necessary to receive two doses to achieve the 90 percent preventive effects in disease severity.

We also should consider the sustainability of preventive measures. The current situation, in which the government hastily proposes the relaxation of preventive measures but then cancels in favor of extending the existing measures by two weeks, exhausts people. Staggered ease of preventative measures could prevent this. It is also necessary to consider the following steps after vaccinating high-risk groups. 

A return to the past will not occur quickly, and numerous controversies and resurgences may arise. Therefore, we should discuss the continuation of the costly preventive measures. Furthermore, we need to review whether measures, such as self-quarantine, blocking inflows from foreign countries, epidemiological investigations, and large-scale tests, are needed.

To live with Covid-19, we also need to prepare future countermeasures to be implemented.

In addition to booster vaccination, the government must prepare the medical system and resources necessary for coexistence with Covid-19 in the second half of this year. The battle will not end easily.

<The writer is a professor of the Department of Preventive Medicine, Gachon University College of Medicine. This article was originally published in the Journal of Korean Medical Science. >