South Korea's National Medical Center on Monday released an interim vaccine report showing that neutralizing antibodies had been formed in all those surveyed.
Research carried out on 50 of its employees all of whom were given the Pfizer vaccine showed that 62 percent developed neutralizing antibodies three weeks after their first dose and all had the antibodies one week after the second dose.
The National Medical Center also reported that the fatality rate for the past two months has fallen to zero.6-9 percent.
This is almost half when compared to the pandemic as a whole at 1.4-9 percent.
It added that 70-percent of hospital beds for critically ill patients are now available.
But, the chief of the country's central clinical committee on new infectious diseases, Oh Myoung-don, says that even after 70 percent of the population is fully vaccinated it is unlikely that herd immunity will be achieved.
He added in a press briefing on Monday that Pfizer's vaccine efficacy of 95 percent refers to the prevention of the disease not the prevention of the virus being spread to other people.
He also said that not knowing how long immunity will last is another factor.
Meanwhile, South Korea confirmed 488 new COVID-19 cases on Monday the first time in a week that the number has fallen below 500.
But this does not necessarily mean that the spread of the virus is slowing down as the drop was in part due to fewer tests being done on the weekend.
Of Monday's 465 locally transmitted cases, more than 40 percent of local transmissions were from outside the capital region.
This raised concerns among health officials that the virus is spreading all across the country.
The government warned that in order to contain the outbreak, and to stop variants from spreading there should be fewer private gatherings in May.
Also, for two weeks starting Monday, the education ministry is trialing testing teams conducting PCR tests in schools for anyone wishing to receive one.
This will be expanded nationwide if the test-run proves effective in Seoul.
Bae Eun-ji, Arirang News.