Although varicella vaccines have been available for many years, varicella remains among the most common infectious diseases, with tens of thousands of reported cases annually.
Associate Professor Pham Quang Thai – Deputy Head of the Department of Infectious Disease Control, National Institute of Hygiene and Epidemiology, speaking at the conference – Photo: THU HIEN
On May 9, the Vietnam Association of Preventive Medicine organised a scientific conference entitled: “Varicella – Second-Generation MAV/06 Strain Vaccine and Updates from the World Health Organization (WHO)”.
Associate Professor Pham Quang Thai – Deputy Head of the Department of Infectious Disease Control, National Institute of Hygiene and Epidemiology – stated that more than 4,200 deaths from varicella are reported worldwide each year.
In the Asia-Pacific region, the disease has shown a shifting epidemiological trend toward adults, with increasing severity and complications. Varicella is highly contagious and can even be transmitted during the incubation period before symptoms appear. A single infected individual may transmit the virus to 12–18 others.
In Viet Nam, varicella consistently ranks among the top five most common infectious diseases. However, public attention is often heightened only during school outbreaks, whereas under normal circumstances, awareness generally remains limited.
In addition, varicella vaccination has not yet been included in the National Expanded Programme on Immunization (EPI). Individuals must therefore pay out of pocket for vaccination, leading many localities to focus primarily on outbreak surveillance rather than implementing widespread vaccination programmes.
According to statistics from 2010 to 2024, Viet Nam has recorded a substantial number of varicella-related hospitalisations. During peak years such as 2018, more than 63,000 cases were reported, with incidence typically increasing from February to May.
However, since 2023, the number of varicella cases has shown an upward trend again, indicating that the risk of outbreaks remains present if high and consistent vaccination coverage is not maintained across communities.
In addition to severe complications such as encephalitis, pneumonia, and neurological damage, varicella may also result in significant scarring and, in some cases, death. High-risk groups, including pregnant women, newborns, and immunocompromised individuals, require particular protection.
Another notable concern is that the varicella virus can remain dormant within the nervous system and later reactivate as herpes zoster (shingles). Previously, shingles was commonly considered a disease affecting older adults; however, dermatology hospitals are now reporting increasing numbers of very young patients, including individuals aged only 18–20 years, primarily associated with stress and immune suppression.
Responding to the question of why varicella-related hospitalisation rates in Viet Nam continue to rise despite the long-standing availability of vaccines, Associate Professor Thai attributed this trend to gaps in vaccine coverage, misconceptions that varicella is a mild disease, and delays in completing recommended vaccination schedules.
Currently, vaccine accessibility in major cities such as Ha Noi and Ho Chi Minh City has improved significantly. Surveys indicate that approximately 90% of the population has access to vaccination services.
Nevertheless, varicella vaccine uptake remains suboptimal, as many parents prioritise other vaccines while overlooking varicella vaccination. As a result, school outbreaks, severe complications, and fatalities continue to be reported.
Regarding vaccination timing, Associate Professor Thai noted that vaccination may now be administered as early as 9 months of age in outbreak situations. However, from an immunological perspective, 12 months of age remains the optimal timing for vaccination.
This is because infants retain maternally derived antibodies during the first months of life. If vaccination is administered too early, the immune response may not be fully optimal. Multiple studies have demonstrated that vaccination at 12 months of age or older induces substantially stronger immunity compared with vaccination at 9 months of age.
| Dr Do Thien Hai – Deputy Director of the Center for Tropical Diseases, National Children’s Hospital – stated that the disease spreads very easily, particularly as the number of immunocompromised children continues to increase.
“We regularly receive paediatric patients with leukaemia, haematological disorders, bone marrow transplants, or prolonged immunosuppressive therapy. Just one infected individual entering the treatment ward can pose a very high outbreak risk,” Dr Hai explained. Importantly, infected children are capable of transmitting the virus even before the onset of rash. In most cases, children are only identified and kept home from school once vesicular lesions appear, but transmission has often already occurred beforehand. Based on epidemiological data in Viet Nam, Dr Hai recommended prioritising vaccination and protection for children under 10 years of age, particularly those aged under 5 to 9 years, who represent the age group with the highest disease incidence. |
source: tuoitre.vn
