A health worker prepares a Covid-19 vaccine shot in HCMC,
August 15, 2021. Photo by VnExpress/Thanh Nguyen 

Several current Covid-19 breakthroughs resulted due to the body not having enough time to produce enough antibodies following the second vaccine shot, doctors said. 

Among over 500 Covid-19 patients being treated at 175 Military Hospital, about 20 percent have received one vaccine shot within four weeks before their diagnoses, while nearly 4 percent have been fully vaccinated.

Vu Dinh An, deputy head of the hospital's ICU department, said a hospital survey revealed around 3.8 percent of coronavirus cases have been fully vaccinated, though their second shots would have needed at least 15 days to reach their full potential.

"Those who receive their first Covid-19 vaccine shot within under four weeks don't have enough time to generate enough antibodies, resulting in high infection rates. Those who are fully vaccinated are much less likely to get Covid-19," said An, adding vaccinated patients saw milder symptoms than those who were unvaccinated.

Nguyen Hong Son, director of the hospital, said the chance of being infected remains high if the body doesn't have enough time to generate the necessary amount of antibodies. He also noted that fully vaccinated individuals are highly protected, preventing their symptoms from becoming severe.

At Cho Ray Hospital, several Covid-19 patients have also had either one or two vaccine shots but not enough weeks have passed. The hospital did not officially tally the number of such cases.

Le Quoc Hung, head of the Tropical Disease Department at the hospital, said those who have received one shot have only just begun to produce antibodies, which are not enough to provide complete protection. They are still susceptible to infections and severe symptoms at roughly the same rate as unvaccinated individuals, he added.

"Those who have had two shots within under four weeks can still be infected and see their symptoms become severe, especially those with underlying conditions," Hung said, adding that the protection one receives also depends on the type of vaccine.

"One cannot let your guard down, even after vaccination," he stressed.

Nguyen Van Vinh Chau, deputy director of the Ho Chi Minh City Department of Health, said there is no vaccine that can provide absolute protection against viruses. But they will generate antibodies, which prevent viruses from gaining access to cells and stave off diseases. Therefore, vaccinated individuals will be less likely to experience severe symptoms and death.

"Some people believe receiving two vaccine shots means not getting Covid-19, which is wrong," said Chau. Vietnam and other countries have already recorded breakthrough cases, as more variants show up and some of them may prove to be resistant against vaccines.

Vaccinated people still need to abide by coronavirus control measures like wearing masks and keeping a safe distance to avoid infection, Chau concluded.

Vietnam has recorded 457,883 local Covid-19 cases since the fourth coronavirus wave hit the country in late April. Over 11,000 patients have died so far.

The country has vaccinated around 20 million people with at least one Covid-19 vaccine shot. Around 2.6 million people are now fully vaccinated.