The third wave of the COVID-19 pandemic is not over yet in Korea, experts said Sunday, calling on public health officials to keep social distancing measures in place to avoid a new surge in cases.

For the sixth consecutive day on Saturday, Korea’s single-day case count exceeded 400 -- reaching 459, of which 436 were locally transmitted and 23 imported, according to government statistics. The cumulative number of cases stood at 95,635.

Although the Ministry of Health and Welfare said a week ago it planned to ease COVID-19 rules in the spring, preventive medicine professor Dr. Ki Mo-ran, who is advising the government’s social distancing policy, says recent statistics put any further reopening in doubt.

She said in a phone call with The Korea Herald on Sunday afternoon that in fact, Korea needs to “scale up efforts” to curtail the infection rate to the pre-third wave levels.

“The country is still seeing numbers similar to the counts in late November, just before it saw a spike over 1,100 daily cases. It’s too early to start unlocking restrictions when we are still not past the third wave of the pandemic,” she said.

In the past week, the number of newly identified community cases per day has averaged at 428.3, qualifying for the second-strictest restrictions in the five-tier social distancing scheme. The country had moved to less strict social distancing tiers in mid-February, with the third and middle tier of social distancing implemented in and around the capital, and for the rest of the country, the second-least restrictive tier.

Ki said Korea needs to expand testing given that about a third of local patients are without symptoms at the time of diagnosis. The test positivity rate was over 1.4 percent, when ideally it should be kept below 1 percent, she said. On Saturday, this rate has jumped to 2.34 percent.

“Similar figures are being reported consistently even on weekends when testing nearly halves, which means that there are probably far more cases in the community going undetected.”

Other projections say COVID-19 cases will probably take an upward trajectory unless more restrictions are put in place.

COVID-19 modeling team at the National Institute for Mathematical Sciences said in Friday’s report that if the current level of social distancing is maintained, the number of patients diagnosed per day could near, or rise above 500 later this month. The modelers based this estimate on the R0, or the average number of secondary cases generated per case, of around 1.04-1.22. An R0 value higher than 1 indicates that the rate of spread is likely to increase.

Former Korea Centers for Disease Control and Prevention Director Dr. Jung Ki-suck said what Korea is seeing now “might be a trough before another peak.”

“Our mistake is not having been able to implement mitigation efforts in time and then removing them too quickly before the situation stabilized,” he said. Social distancing of a higher intensity “appears necessary” at least in the Seoul metropolitan area, which has been Korea’s pandemic epicenter since last summer, he added.

He said the remainder of the year would be “all about balancing reopening and vaccinations.”

“The important thing is to keep any rise in infections at bay until vaccination efforts start to pay off.”

On Saturday, vaccinators across the country delivered COVID-19 vaccines to 3,487 people. So far Korea has inoculated 587,884 people with their first doses -- 561,785 people with the AstraZeneca vaccine, and 26,099 with Pfizer’s.

The mass vaccination campaign began here on Feb. 26 with 1.5 million doses from AstraZeneca and 117,000 doses from Pfizer. Korea is aiming to vaccinate roughly one fifth of its population of 10 million people by the end of June.

The vaccine rollout in the second quarter of the year will extend to residents 65 years of age or older at long-term care facilities as well as public officials flying for essential purposes and airline cabin crew, health officials hinted ahead of the weekend, with the details set to be announced Monday.

There have been 8,520 reports of suspected side effects among vaccine recipients as of Saturday. The vast majority, or 8,423, of those cases involved known symptoms such as fever, body aches and discomfort around the injection site that went away within a few days.

The other few were classified as more serious, but their links to the vaccines are not proven. Health officials said Saturday the 74 reports of reactions “akin to anaphylaxis,” or severe allergy, did not fit the case definition. One report of a seizure, six of hospitalizations and 16 of fatal outcomes were mostly in patients with chronic medical conditions.

“In all likelihood, there is no causal relationship between the reports and the vaccines themselves,” said virology professor Dr. Paik Soon-young of Catholic University of Korea. More than 300 million doses of COVID-19 vaccines have been administered globally, with no evidence to date to suggest the reported “adverse events” were a result of vaccination, he said.

By Kim Arin (arin@heraldcorp.com)