Recently, reports regarding 53 healthcare workers in Ho Chi Minh City who tested positive for the SARS-CoV-2 virus after receiving two doses of the COVID-19 vaccine have caused considerable public anxiety and concern. To provide a clearer perspective on this issue, a reporter from VietTimes had an exchange with Dr. Pham Quang Thai – Deputy Head of the Department of Infectious Disease Control, National Institute of Hygiene and Epidemiology (NIHE), and a member of the Rapid Response Information Team of the National Steering Committee for COVID-19 Prevention and Control.
- Currently, reports that dozens of healthcare workers at the Hospital for Tropical Diseases in Ho Chi Minh City contracted COVID-19 despite being vaccinated have caused widespread public concern. How do you evaluate this situation?
Dr. Pham Quang Thai: I affirm that dozens of healthcare workers at the Hospital for Tropical Diseases in Ho Chi Minh City were only infected with the SARS-CoV-2 virus, rather than developing COVID-19, after receiving two doses of the COVID-19 vaccine.
COVID-19 is a disease caused by the SARS-CoV-2 virus. A diagnosis of the disease requires clinical manifestations and symptoms (such as fever, cough, shortness of breath, etc.). However, following two doses of the COVID-19 vaccine, only one of these individuals exhibited symptoms of a runny nose, and a positive test result subsequently prompted hospital-wide screening. The remaining personnel were merely infected with SARS-CoV-2 without exhibiting distinct symptoms.
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Dr. Pham Quang Thai transporting COVID-19 vaccines to support provinces experiencing outbreaks (Photo provided by the interviewee) |
In reality, four individuals experienced a temporary reduction in their sense of smell, and a few reported feeling fatigued, but they recovered rapidly. Therefore, since these healthcare workers did not display clinical symptoms of the disease, it is inaccurate to state that they contracted COVID-19. While it is accurate to say they were infected with the virus, claiming they developed COVID-19 is incorrect. This is analogous to how many people test positive for diphtheria bacteria in their pharynx without actually developing diphtheria; they are merely carriers of the bacteria.
Following COVID-19 vaccination, healthcare workers develop immunity to protect their bodies against severe forms of the disease. The primary objective of COVID-19 vaccines is to help individuals prevent severe illness and avoid the risk of hospitalization or death. Nevertheless, vaccination does not completely eliminate the risk of contracting the SARS-CoV-2 virus.
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Healthcare workers preparing to administer COVID-19 vaccines (Photo: Minh Thuy) |
To date, even the world's leading COVID-19 vaccines cannot entirely prevent vaccinated individuals from contracting SARS-CoV-2. This applies not only to COVID-19 vaccines but also to all long-established vaccines—such as those for diphtheria, pertussis, tetanus, influenza, varicella, and Japanese encephalitis—which still cannot completely prevent post-vaccination viral infection, even when administered in full schedules.
Therefore, I reiterate that after receiving a COVID-19 vaccine, individuals still retain the possibility of viral infection while being protected against developing the disease.
- Could you share insights on the protective efficacy of COVID-19 vaccines against SARS-CoV-2 and its variants?
Dr. Pham Quang Thai: Recently published studies evaluate the efficacy of COVID-19 vaccines in preventing severe illness in Vietnam at up to over 90% at present. Statistics indicate that over 90% of vaccinated individuals have been protected from severe disease and avoided the risk of hospitalization. However, contracting the SARS-CoV-2 virus post-vaccination remains unavoidable. The rate of SARS-CoV-2 infection following COVID-19 vaccination can reach up to 40%. In other words, COVID-19 vaccines can only prevent SARS-CoV-2 transmission by approximately 60–80%, depending on the vaccination regimen.
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Dr. Pham Quang Thai inspecting individual batches of COVID-19 vaccines prior to dispatch to provinces (Photo provided by the interviewee) |
- Could you inform us whether healthcare workers who contract COVID-19 after two vaccine doses are at risk of developing severe illness and transmitting the disease to others?
Dr. Pham Quang Thai: Following the second dose of the COVID-19 vaccine, very few individuals develop severe illness. To date, no cases in Vietnam have involved severe disease onset one month or more after receiving the second vaccine dose, with the clearest evidence observed at the Hospital for Tropical Diseases in Ho Chi Minh City. To date, our country has administered over 1 million doses of COVID-19 vaccines to frontline forces and priority groups in accordance with Government Resolutions. Following vaccination, no cases of severe illness have been recorded.
Regarding the risk of contracting COVID-19 and subsequently transmitting it to others after two vaccine doses, this is very difficult to assess conclusively. Following SARS-CoV-2 infection, the viral load shed by vaccinated individuals is lower than that of unvaccinated individuals. This phenomenon has been observed in COVID-19 patients in Vietnam and globally. Furthermore, the duration of viral shedding is shorter; at the Hospital for Tropical Diseases, among several dozen infected individuals, 21 ceased shedding the virus after only a few days, indicating that the infection was transient and posed no danger to others. Consequently, experts suggest that because viral loads in vaccinated individuals are lower than in unvaccinated ones, the risk of transmitting the virus to others is significantly reduced. According to the World Health Organization (WHO), the transmission rate among vaccinated individuals is markedly lower than among completely unvaccinated individuals.
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SARS-CoV-2 virus (Photo: Minh Thuy) |
- It has been suggested that international medical literature indicates vaccination reduces disease severity upon infection. Where can this literature be found, and who conducted these studies?
Dr. Pham Quang Thai: An increasing body of medical literature confirms these findings. Allow me to cite some of the most recent publications, such as those by Public Health England (PHE) available at: https://www.openaccessgovernment.org/astrazeneca-vaccine-delta/112884/, which demonstrate that the AstraZeneca vaccine protects vaccinees against severe illness by up to 92% against the Indian variant (Delta).
Previously, several older publications stated that this vaccine provided 100% protection against severe illness and death from non-Delta strains. The report link for this clinical trial is available here:
https://clinicaltrials.gov/ct2/show/NCT04516746?term=NCT04516746&draw=2&rank=1
Another report, scheduled for official publication soon, demonstrates that even a single dose of this COVID-19 vaccine triggers antibody and cellular immune systems to protect recipients, particularly with the AstraZeneca vaccine:
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3825573
- Thank you very much for this conversation!