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Updated: Jan 16, 2022

Are healthcare professionals aware of, and faithfully fulfilling, their duty to report all serious adverse events (“AEs”) even if they are unsure about whether the vaccine has caused them? If not, what are the implications, especially on any individual’s risk-benefit analysis on whether to vaccinate?


On 20 November last year, I wrote to the Health Sciences Authority (“HSA”) with the following 3 important questions (I have renamed the title of the document as “3 Questions”, rather than the original “3 Unanswered Questions”, as the HSA subsequently replied to me on 30 November 2021).

Enclose a copy of the PDF of my 3 questions.

Download PDF • 108KB

The HSA’s reply to me on 30 November 2021 is set out below.


Dear Mr. Chan,

We refer to your email to [the HSA]. Thank you for your feedback.

HSA actively monitors the safety of the COVID-19 vaccines to ensure that their benefits continue to outweigh the risks when used in a pandemic. This is achieved through our post-market surveillance programme to monitor the safety, quality and efficacy of health products marketed in Singapore, including vaccines to detect any potential safety concerns so that the necessary actions can be taken to ensure that the health products remain safe for use.

One of the pillars of our vaccine AE monitoring programme is the reporting of suspected adverse events (AEs) by local healthcare professionals to HSA. Healthcare professionals are required to report all serious AEs even if they are unsure about whether the vaccine has caused them. In addition, all AEs to any medicines, including vaccines that are captured in the medical records of patients are also routed to HSA for analysis. This ensures that HSA has a comprehensive overview of the AEs experienced by our patients.

Members of the public can also report AEs experienced after COVID-19 vaccination to HSA. These reports supplement the AEs that are reported by healthcare professionals. We review them to determine if there are any serious or unexpected AEs. These reports are analysed in totality with the AE reports from the healthcare professional. Based on the public AE reports received to date, they are generally non serious and consistent with what is currently known with the COVID-19 vaccines globally.

In addition to monitoring local AE reports, HSA also draws on its network of regulatory counterparts overseas and the World Health Organisation (WHO) International Drug Monitoring Programme to monitor for safety signals relating to the COVID-19 vaccines used in Singapore. These collaborations and information exchange facilitate better signal detection through the strength of aggregated review of global reports and enable HSA to identify and respond promptly to any potential safety signals that may occur in our population. HSA considers the totality of data from all sources before drawing any evidence-based conclusions on the safety of the COVID-19 vaccines. HSA will communicate safety signals or potential safety concerns we are monitoring closely in our monthly safety update reports to the public. Thus far, no deaths have been attributed to the COVID-19 vaccines. The benefits of receiving COVID-19 vaccines continue to far outweigh the risks of vaccination in a pandemic.

I hope the above addresses your concern.

Thank you.

Best Regards,

[HSA representative]

[Emphasis in bold added]


For this article, I will provide a short commentary on the duty of healthcare professionals to report all serious AEs.

Important Note: I am a pro-vaccination, fully vaccinated, concerned citizen of Singapore. Everyone, especially those who are older and vulnerable, should seriously consider the option of getting vaccinated to protect themselves from serious Covid or death. Nothing in this article shall be construed as encouraging anyone to remain unvaccinated or to downplay the seriousness of Covid for those who are more vulnerable to it. Nevertheless, it

is of utmost importance that any decision to vaccinate must be made voluntarily, free from any duress or coercion.


First, the HSA has unequivocally affirmed that:

Healthcare professionals are required to report all serious AEs even if they are unsure about whether the vaccine has caused them.”

I would argue that healthcare professionals have a duty to report serious AEs even if they think that causality is unlikely (and not only if they are unsure). This is evident from the fact that the reporting form to the HSA contains 6 options on causality assessment, one of which is “unlikely”, and two others are “unconfirmed” and “not known” (as explained in my “3 Questions to the HSA” above).

This is also the reporting standard in US with regards to the administration of Covid-19 vaccines, i.e. there is a duty to report serious AEs “regardless of whether the reporter thinks the vaccine caused the AE” (as explained in my “3 Questions to the HSA” above).

Second, it is unclear what the actual practice on the ground is.

By way of a question (and not an assertion of fact), insofar as there are healthcare professionals who are unaware of the above reporting obligation and/or do not discharge it, then there is a real risk of underreporting. This goes back to Factor 5 of Table 1, “Proposed Framework of Factors for Risk-Benefit Analysis” (see my previous article titled “The Decision to Vaccinate: The Risk-Benefit Analysis Re-Analysed”).

Third, if there is a real risk of underreporting, then Factor 5 which relates to “Sensitivity” (of the reporting system of adverse events) will lean against vaccination.

Let me elaborate. Insofar as the reporting system is not sensitive enough to pick up on all serious AEs, hitherto unknown AEs will remain unknown and unstudied. Without relevant studies appearing in peer-reviewed articles, causality association is harder to establish. Even if a serious AE is causally associated with the vaccine, the person may find it hard to prove causality (at least until the peer-reviewed science catches up, which needs time), and/or any underreporting will reduce the likelihood of safety signals being picked up on. In any event, confidence in the system, to accurately and sensitively detect all safety signals, will drop.

And all these lean against vaccination, and against any mandatory vaccination (and in turn, any VDS).

On the other hand, if all healthcare professional are faithfully reporting all serious AEs even if their personal view of causality is “unlikely”, “unconfirmed” or “not known” – then this Factor 5 (and assuming that all other sub-factors in Factor 5 together with the other proposed 9 Factors in Table 1 are satisfied) leans towards vaccination.

Relevance to the Vaccinated Majority

There are some unvaccinated persons (or even vaccinated ones) who are concerned about the potential lack of sensitivity of the reporting system. These are legitimate concerns, especially in any person’s risk-benefit analysis. And whether Singapore’s reporting system is truly sensitive, is a debatable issue, because it depends a lot on the practice on the ground, notwithstanding the HSA’s official position.

And because this is debatable – as part of the vaccinated majority, we should give room for the unvaccinated, and to respect their right, to make their own risk-benefit analysis in deciding whether to vaccinate.

Dominic Chan

P.S. For the sake of completeness, please see HSA’s latest Safety Update #8 published on 20 December 2021 (reporting up to 30 November 2021).

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