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Safety updates on COVID-19 vaccines

Find out about suspected adverse events which have been reported to HSA following COVID-19 vaccination in Singapore.


HSA actively monitors the safety of COVID-19 vaccines authorised in Singapore to ensure that the benefits of these vaccines continue to outweigh the risks and that they remain safe for use. This is done through adverse events (AEs) monitoring systems to detect any potential safety signals so that relevant measures can be taken expeditiously. 

The COVID-19 vaccines* currently authorised and rolled-out are as follows:

Vaccines Authorisation date  Vaccination roll-out date 
Pfizer-BioNTech/Comirnaty COVID-19 vaccine 14 December 2020 30 December 2020
Moderna/Spikevax COVID-19 vaccine 3 February 2021 12 March 2021
Sinovac-CoronaVac COVID-19 vaccine 23 October 2021 18 June 2021
Nuvaxovid COVID-19 vaccine 3 February 2022 18 May 2022

*Pfizer-BioNTech/Comirnaty is registered as a therapeutic product by HSA on 10 December 2021. Moderna/Spikevax, Nuvaxovid, Sinovac-CoronaVac are authorised under the Pandemic Special Access Route. 

The following report provides an overview of suspected AEs that have been reported to HSA by healthcare professionals following the use of COVID-19 vaccines. The report also includes HSA's assessment of these reported AEs.

Key Updates (as of 31 August 2022)

Date of publish: 19 Sep 2022

i) mRNA COVID-19 Vaccines

  • A total of 10,289,262 primary doses, 4,420,853 first booster doses and 439,383 second booster doses of the mRNA vaccines have been administered. The reporting rates of AEs and serious AEs for the mRNA vaccines remained rare. The serious AE reporting rates for the first and second booster doses were at 0.004% (162 reports) and 0.0005% (2 reports), respectively, which were lower compared to the primary doses at 0.009% (916 reports).

  • There were no new safety findings since the previous update published in June 2022 (please refer to the previous HSA’s COVID-19 Vaccine Safety Update for details).

ii) Nuvaxovid COVID-19 Vaccine

  • The vaccination programme for Nuvaxovid COVID-19 vaccine was rolled out on 18 May 2022, with 18,073 doses being administered as of 31 August 2022.
  • Locally, 28 AE reports were received of which 82% (23 reports) were non-serious ones which included allergic reactions such as rash and eyelid swelling, numbness, vasculitis (inflammation of blood vessels), dizziness and chest pain. These were largely consistent with what were reported in the clinical studies or with other COVID-19 vaccines. There were 5 serious AE reports (0.03% of administered doses) which included 4 cases of anaphylaxis and 1 case of serious allergic reaction. These occurred in susceptible individuals who had previous allergic reactions or adverse effects to Pfizer/Comirnaty and Sinovac-CoronaVac COVID-19 vaccines, as well as a history of drug or food allergies. All the patients have recovered from the serious adverse reactions.
  • Anaphylaxis is a rare and potentially life-threatening allergic reaction that can occur following vaccination in certain susceptible individuals. As with the mRNA vaccines, safeguards such as pre-vaccination screening, post-vaccination observation period and ensuring that all vaccination centres are medically equipped and staffed by qualified medical professionals are in-place to mitigate this risk.
  • HSA is also monitoring myocarditis and pericarditis AEs closely. To date, no local AE reports of myocarditis or pericarditis have been received with the Nuvaxovid COVID-19 vaccine. A small number of reports of myocarditis and pericarditis following vaccination have been reported overseas where exposure to Nuvaxovid COVID-19 vaccine is higher. As a precautionary measure, persons who are vaccinated with the Nuvaxovid COVID-19 vaccine should avoid strenuous physical activity or exercise for two weeks after vaccination to mitigate the potential risk of myocarditis. It is important to note that COVID-19 infection is known to be associated with myocarditis. Based on published literature, 40 extra myocarditis events per million persons were observed following COVID-19 infection.


iii) Sinovac-CoronaVac and Sinopharm COVID-19 Vaccines

  • A total of 635,420 doses of the inactivated vaccines have been administered as of 31 August 2022. The serious AE reporting rate remained rare at 0.006% (39 reports).
  • As with the case of mRNA vaccines, there were no new safety findings for the inactivated vaccines since the last update published in June 2022 (please refer to the previous HSA’s COVID-19 Vaccine Safety Update for details).

Based on the local AE reports received, most of the AEs are largely expected with vaccination and reflect what has been reported globally. Overall, based on the data to date, the benefits of the Pfizer-BioNTech/Comirnaty, Moderna/Spikevax, Nuvaxovid and Sinovac-CoronaVac COVID-19 vaccines continue to outweigh the known risks. 

For more information on COVID-19 vaccination in Singapore, please refer to MOH website (