Ho Chi Minh City resident Nguyen Thanh Nhan, 66, received a kidney transplant a year ago. His health improved after the surgery, so he was eligible to receive two Covid-19 vaccine shots. Following the inoculation, however, his antibody levels were scant as his body didn’t seem to produce any immune response to the vaccine.

As the Covid-19 pandemic outbreaks show no signs of easing, Nhan has been wary of contracting the virus, despite having taken careful preventive measures. He has found it difficult to return to a new normal life or participate in any communal activities. High-risk people like Nhan are likely to develop severe illnesses if they are infected with Covid-19.

Prof. Dr. Ngo Quy Chau, President of the Vietnam Respiratory Association, Medical Director of Tam Anh Hanoi General Hospital, said: "Despite being fully vaccinated, many patients continue to be anxious, having to isolate themselves from their loved ones and limit their social interactions. In fact, many of them don’t even dare leave the house for a medical checkup at the hospital. They’re still extremely worried that their body couldn’t generate an adequate immune response after vaccination like a healthy person."

As a respiratory disease expert, he said patients with lung cancer, severe asthma, and interstitial lung disease who need to take corticosteroids regularly (with or without other underlying medical conditions) are at high risk of severe disease progression and death if infected with Covid-19.

Assoc. Prof. Dr. Pham Van Bui, Chairman of the HCMC Kidney Dialysis Association, Senior Lecturer at Pham Ngoc Thach Medical University, Advisor of Nguyen Tri Phuong Hospital in HCMC, said the hospital is treating more than 200 patients who are currently on dialysis. These patients are in the priority group to receive a full two-dose vaccination regimen and a third booster shot for enhanced protection.

"Those with underlying medical conditions, if immunocompromised, are at risk of severe symptoms if they contract Covid-19, regardless of whether they have received two or three vaccine doses," said Prof. Bui.

Because of the pandemic, patients with cancer, organ transplants or in need of surgical interventions, have had limited access to critical treatment services, worsening their conditions. Many of these patients have also been reluctant to go to the hospital, as cases and deaths surged across the country while they have yet to be fully protected against Covid-19.

Despite suffering from nasopharyngeal cancer and currently undergoing treatment, Dang Van Mieu, 64, from Can Giuoc District, Long An Province, decided that he would stop visiting the hospital. For the whole year since Covid-19 broke out, he was afraid to travel to Ho Chi Minh City to get his cancer examined. Only towards the end of 2021, as the outbreak was temporarily under control, did he resume his chemotherapy sessions to treat the tumor.

"When most people have begun to live safely with the virus, I feel like I'm being left behind. After such a long time of treatment delay, the doctor said that my tumor has spread and active treatment will be needed," Mieu said.

Many countries currently assess the risk of Covid-19 primarily based on the number of hospitalizations and deaths, instead of the number of infection cases. Those hospitalized or who died due to Covid-19 were mostly unvaccinated or immunocompromised with several underlying conditions. According to The New York Times, it’s estimated that 7 million people in the U.S. are living with a compromised immune system due to cancer treatment, organ transplants or other conditions.

Although the current Covid-19 vaccination program has been effective in protecting most of the society, researchers estimate that about 2-3 percent of the world's population is immunocompromised. Depending on their underlying conditions and the medications they’re taking, these populations may never be able to produce an optimal immune response, even if they are fully vaccinated.

Explaining the mechanism of the immune system, Prof. Chau said that when receiving a vaccine, the human body is exposed to antigens, triggering an immune response with the participation of T cells, B cells and antibodies, thus forming immunological memory. The integrity of these immune system components is essential to generate optimal active immunity.

However, for patients with blood cancer, those undergoing chemotherapy, organ transplants, dialysis, or taking immunosuppressive drugs, components of their immune system would be affected by their own illnesses or treatment side effects. As a result, their bodies are unable to produce robust antibodies, reducing or impairing their ability to generate active (vaccine-induced) immunity against diseases.

In addition, there remain individuals who are not recommended to take a Covid-19 vaccine, such as people who have experienced anaphylaxis after vaccination, or advised against vaccination by the manufacturers. Immunocompromised people who have been vaccinated but live or work in high-risk environments also need an extra layer of protection.

According to Assoc. Prof. Dr. Huynh Nghia, Head of Hematology Department and Deputy of Medical Faculty at HCMC University of Medicine and Pharmacy, Head of Children's Clinical Hematology Department of HCMC Blood Transfusion and Hematology Hospital, if this group of people, which accounts for 2-3 percent of the world's population, does not receive sufficient protection against Covid-19, they could become potential virus incubators from which new variants emerge and evolve, making it even more difficult for the world to stem this pandemic. The need to protect these vulnerable groups, therefore, is more urgent than ever, to help reduce the burden on our healthcare system and stop the pandemic from progressing.

"Although Vietnam has not had official statistics, there remains a number of people who are unable to be vaccinated or couldn’t mount a sufficient immune response after receiving a Covid-19 vaccine. This is the 'gray area' in all countries’ vaccination programs. Many countries are researching methods to protect this vulnerable group who may need an additional, or more immediate, layer of defense against Covid-19," said Prof. Bui.

Scientists around the world are working on different Covid-19 solutions to protect these vulnerable populations. One of the latest innovative therapies is monoclonal antibodies that are manufactured from human cells or donated by patients who have recovered from Covid-19.

"As opposed to ‘active immunity’ which involves the body generating antibodies by itself following vaccination, monoclonal antibodies create ‘passive immunity’, whereby we inject pre-made antibodies into the body. While it can take up to a few weeks for the body to produce antibodies on its own after being vaccinated, an injection of monoclonal antibodies will provide nearly instant protection within a few hours, and can last from several months to a year," Prof. Nghia explained.

After being delivered into the body, the monoclonal antibodies would identify and bind to distinct sites on the SARS-CoV-2 virus spike proteins to attack the virus directly, preventing it from invading other cells and thereby stopping the disease from spreading. According to Prof. Chau, this mechanism creates a layer of "instant defense" for the body to enhance protection.

A few monoclonal antibodies have been approved by the Food and Drug Administration (FDA) in the U.S. and other countries for post-exposure prophylaxis and outpatient treatment of Covid-19.

In December 2021, the FDA granted an Emergency Use Authorization (EUA) for AstraZeneca's long-acting antibody "cocktail". Delivered by intramuscular injection, this is the first antibody therapy approved for the prevention of Covid-19 (pre-exposure prophylaxis) in moderately to severely immunocompromised adults and adolescents (12 years of age and older weighing at least 40 kg), or those for whom vaccination is not recommended.

Recently, it also became the first monoclonal antibody to be granted a special import approval by the Ministry of Health for the pre-exposure prophylaxis of Covid-19 in Vietnam. This antibody therapy is expected to soon arrive in Vietnam to protect those who are not infected with Covid-19 and who have not had a recent exposure to a positive case, according to the indication. "Many studies have shown promising results of using monoclonal antibody therapy to increase protection for individuals who happen to be in the 'gray zone', or those vaccinated but live or work in high-risk environments. Alongside vaccines, monoclonal antibodies are expected to be a ‘new weapon’ to help control Covid-19," said Prof. Bui.

According to Prof. Chau, these high-risk groups are strongly recommended to follow the government’s "5K safety measures". He expects that monoclonal antibodies will bring hope to these patients, helping them feel protected against Covid-19 and more at ease when participating in social activities.

All patients’ names have been changed for the purpose of anonymity.

Kim Uyên