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Updated as of 10 Aug 2021

Safety and Efficacy of the COVID-19 Vaccine


Which vaccines are approved for use in Singapore? Which of these vaccines are included in the national vaccination programme?


The Health Sciences Authority (HSA) has assessed that the Pfizer-BioNTech/ Comirnaty and Moderna COVID-19 Vaccines meet safety and efficacy standards. HSA has authorised their use locally under the Pandemic Special Access Route (PSAR) which facilitates early access to vaccines and medicines during a pandemic, such as COVID-19. 

The Expert Committee on COVID-19 Vaccination (EC19V) has also recommended the use of the Pfizer-BioNTech/ Comirnaty and Moderna COVID-19 Vaccines by the population, and are the 2 vaccines used in the national vaccination programme*. Only vaccines deemed suitable for use in target population subgroups, and where overall benefits outweigh the known risks, are recommended for use by the Expert Committee.

*Links to Press Releases (27 Dec 2020 and 3 Feb 2021):

1. Expert Committee Submits Recommendations on Singapore’s COVID-19 Strategy



2. Government Accepts Recommendations of Expert Committee on COVID-19 Vaccination



3. HSA Grants Interim Authorisation for Moderna COVID-19 Vaccine in Singapore



4. Second COVID-19 Vaccine Authorised for Use in Singapore


Vaccines for COVID-19 have been approved for use in a shortened timeframe compared to other vaccines or drugs. How can we be sure that scientific rigour has not been compromised?


An accelerated development timeline for vaccines against COVID-19 was possible given the following:


a. Significant investment and dedication of resources from vaccine manufacturers to the ramping up of vaccine production; moreover, the mRNA technology platform had already been in development for many years prior to the COVID-19 pandemic.


b. Strong global partnerships between many different partners including international organisations, governments, researchers and manufacturers;


c. Given the pandemic situation, recruitment for and conduct of the randomised controlled trials to identify the differences in disease risk between those given vaccines and placebo, are able to be conducted more quickly than in the absence of a pandemic.


d. Many trials have performed their trial phases concurrently, allowing for sufficient data to be produced in a shorter time.


Safety, scientific or ethical integrity have not been compromised, and no short-cuts have been made, but the unique circumstances and factors described above have allowed accelerated development.


Emerging real-world and follow-up data on the safety and effectiveness of the mRNA vaccines in other jurisdictions is consistent with the effectiveness of the mRNA COVID-19 vaccines observed in the Phase 3 trial data. This further supports that scientific rigour was not compromised in the development of the mRNA COVID-19 vaccines.

How effective is the vaccine? How long does the protection last?


Based on Phase 3 trial data from Pfizer-BioNTech/ Comirnaty and Moderna, the efficacy of the vaccines in preventing symptomatic COVID-19 disease, after completion of the vaccine regimen, is about 95%.


Updated data from the Pfizer-BioNTech/ Comirnaty and Moderna Phase 3 trials on individuals with a follow-up time of at least six months showed that the vaccines continue to be effective for at least six months with no signs of waning protection. MOH will continue to monitor and review further data on the duration of immunity.


If it is a single dose, what will the efficacy be?


Two doses of the Pfizer-BioNTech/ Comirnaty and Moderna COVID-19 vaccines are required to achieve optimal protection against COVID-19. Persons should complete two doses of either the the Pfizer-BioNTech/ Comirnaty and Moderna vaccines, based on the respective vaccination schedules.

Can vaccinated persons get infected with COVID-19? Are they less able to transmit the disease?

The efficacy of Pfizer-BioNTech/ Comirnaty and Moderna COVID-19 vaccines were shown to be about 95% in preventing symptomatic and severe disease. That means that some vaccinated persons may still be vulnerable to infection.

There is also evidence that vaccinated individuals recover faster than unvaccinated persons. There is therefore some increase in protection against onward transmission, even if it is not 100% protection. We continue to monitor the emerging data on the extent to which vaccination will reduce onward transmission of infection.

[Updated 10 Aug 21] Who should not get the mRNA-based COVID-19 vaccines?


The mRNA-based COVID-19 vaccines are not recommended for children under the age of 12 years for Pfizer-BioNTech/ Comirnaty COVID-19 vaccine and children under the age of 18 years for Moderna COVID-19 vaccine until more efficacy and safety data become available for these subgroups. 

Persons with a history of allergic reaction or anaphylaxis to mRNA COVID-19 vaccine or its components SHOULD NOT receive the mRNA-based vaccine again. Anaphylaxis is a severe life-threatening reaction with two or more of the following three criteria:

a) Hives or face/eyelid/lip/throat swelling;
b) Difficulty breathing;
c) Dizziness.

Persons who had history of an allergic reaction or anaphylaxis to other vaccines may be allergic to specific components of vaccines which could also be present in the COVID-19 vaccine. These persons may still be able to receive the mRNA-based COVID-19 vaccine but require consultation with a specialist to determine suitability for vaccination. The vaccination sites will be able to provide the referral to the specialist which will be fully subsidised. These individuals  SHOULD NOT be vaccinated with the mRNA vaccines until they have been evaluated on suitability by the specialist.

Persons who were diagnosed with myocarditis after a dose of mRNA COVID-19 vaccines should also not receive the vaccine again.


Who are considered severely immunocompromised and should not receive the mRNA-based vaccine?

 A:The following are some examples of severely immunocompromised persons, but there may be other examples not on this list.
• Transplant within the past 3 months (solid organ or stem cell)
• Aggressive immunotherapy (e.g. Rituximab) for non-cancer conditions
Such patients can be vaccinated if they have a memo from their treating specialist allowing them to be vaccinated.

If in doubt, patients are encouraged to discuss their suitability for COVID-19 vaccination with their doctor. Individuals will also be assessed by the medical personnel at the vaccination sites for their suitability to receive the vaccination before they are vaccinated.


If a person cannot currently receive the mRNA-based COVID-19 vaccines i.e. is contraindicated against the vaccine, does it mean that the person will not be able to be protected against COVID-19 through vaccination?


Persons for whom the Pfizer-BioNTech/ Comirnaty COVID-19 Vaccine or Moderna COVID-19 vaccine is contraindicated at this time may be able to get vaccinated with these vaccine(s) if data becomes available that it is safe to vaccinate them. Alternatively, they may be able to get vaccinated with other suitable COVID-19 vaccines, when available.

 Can individuals with a history of anaphylaxis to other medications, drugs, food, insect stings, or unknown triggers (idiopathic) take the mRNA-based vaccine? Are they at higher risk of anaphylaxis?
 Individuals with a history of anaphylaxis to other medications, drugs, food, insect stings, or unknown triggers (idiopathic) CAN be vaccinated.

There  is no evidence to suggest that individuals with a history of anaphylaxis to non-vaccine related triggers are at higher risk of anaphylaxis to the mRNA-based vaccines.

Can individuals with a history of NSAIDS-induced angioedema or multiple allergies be vaccinated with the mRNA-based vaccine?


Individuals with multiple allergies CAN be vaccinated, as long as the allergies are non-vaccine related.


Emerging local and international scientific evidence had shown individuals with NSAIDs-induced angioedema or even anaphylactoid reactions to NSAIDS CAN be vaccinated with a mRNA-based COVID-19 vaccine.


Can persons with active cancer be vaccinated?


Cancer Patients Not on Treatment

Persons with active cancer who are NOT on treatment with chemotherapy, radiotherapy or immunotherapy CAN be vaccinated at any available vaccination site. Active cancer not on treatment is defined as:

  • Not being on any of the above treatment in the past 3 months AND
  • Not having planned treatment of the above in the next 2 months

Persons with a history of cancer, who are in remission, CAN be vaccinated at any available vaccination site.


Cancer Patients On Hormonal Treatment

Persons on active cancer hormonal therapy CAN be vaccinated at any available vaccination site.

Cancer Patients on Active Treatment
Persons on active cancer chemotherapy, radiation therapy or immunotherapy can be vaccinated if they have a memo from their treating oncologist/specialist clearing them to be vaccinated.

I have recovered from a COVID-19 infection. Can I take my 2 shots of vaccine now?
 A:Individuals who have had an earlier COVID-19 infection, and have recovered, are recommended to receive a single dose of vaccine no earlier than 3 months after the date of their diagnosis if they had not already completed vaccination previously. There is evidence that a single dose would further boost their immunity against COVID-19.

Can pregnant or breastfeeding women receive the mRNA-based COVID-19 vaccine? 

A:Internationally, a large number of pregnant and breastfeeding women have received a COVID-19 vaccination.  The Expert Committee on COVID-19 Vaccination (EC19V) has examined studies done to monitor women who were vaccinated when they were pregnant, and their babies. These studies were done on women at different trimesters of pregnancy and  there is no evidence to suggest that the Pfizer-BioNTech/ Comirnaty or Moderna COVID-19 vaccine may cause harm to pregnant women or their babies.

Both Pfizer-BioNTech/ Comirnaty and Moderna COVID-19 vaccines are mRNA vaccines. As mRNA vaccines are not live vaccines, they are biologically unlikely to adversely affect breastfed babies. In addition, the breast milk of vaccinated mothers may help to protect their babies from COVID-19 due to antibodies in breast milk. There have also been no vaccine-related side effects reported in the babies who were breastfed by mothers who received the vaccine while breastfeeding.

Will the mRNA-based COVID-19 vaccine cause infertility?


There is currently no evidence that the mRNA-based COVID-19 vaccines can cause infertility in vaccine recipients.


Is COVID-19 vaccination safe for those with chronic illness such as hypertension, high cholesterol and diabetes?


Persons with chronic illnesses are recommended to receive the vaccine for personal protection as well as protecting their loved ones. The study population for Pfizer-BioNTech/ Comirnaty’s and Moderna's phase 3 trials included persons with medical comorbidities, who were at risk of serious, life-threatening disease and death from COVID-19 infection, and demonstrated effectiveness with no safety concerns reported in this group.


Can I receive another (non-COVID-19) vaccine at the same time as COVID-19 vaccine? How long do I have to wait before getting other vaccines? 

A:There is no data on administering COVID-19 vaccine at the same time as other non-COVID-19 vaccines. A minimum interval of 14 days is encouraged before or after any other vaccines i.e. where possible, other vaccines should not be administered 14 days or less before the first dose; or 14 days or less after the second dose of a COVID-19 vaccine.

Can I donate blood after receiving the COVID-19 vaccine?


The Health Sciences Authority (HSA) and the blood bank has implemented a new blood donation eligibility guideline for donors who received a COVID-19 vaccine.  

The deferral period may vary depending on the type of vaccine received or if you developed symptoms after receiving the vaccine.  Please click here  for more information.

 What is myocarditis and pericarditis? Can the vaccine lead to myocarditis and pericarditis?
 A:Myocarditis and pericarditis are inflammatory conditions affecting the heart muscles and the outer lining of the heart, respectively. Patients may present with symptoms such as chest pain, shortness of breath or abnormal heartbeats. Local incidence rates remain low and the cases are usually mild and recover well.
As a precautionary measure, adolescents and men below 30 years of age are advised to avoid strenuous physical activities such as running, weightlifting, competitive sports, or playing ball games for one week after their first and second vaccination doses.


If I am allergic to the first dose of the mRNA vaccine and will not receive my second dose, am I still protected from COVID-19? Will there be suitable alternatives in future for me?


The current mRNA-based vaccines (Pfizer-BioNTech/ Comirnaty and Moderna)'s dosing regimens recommend for 2 doses to ensure that the optimal protection is provided.
Persons who are unable to receive the full 2-doses regimens of the mRNA-based vaccines may have suitable alternatives in future as more vaccine candidates are made available.


I am unsure if it is medically safe for me to be vaccinated. What should I do?


MOH has put in place steps to ensure it is medically safe before you are vaccinated. Before making appointments for vaccination, you will be prompted to complete an online screening form, which contains medical questions to screen out those who are unsuitable for the current COVID-19 vaccines (i.e. Pfizer-BioNTech/ Comirnaty and Moderna). Once you have cleared the online screening, you will be invited to book your appointments for vaccination. In the event that you have booked your appointments but remain unsure if you should receive the vaccine, there will be another round of medical screening conducted at your preferred vaccination site on the day of vaccination. You may seek clarifications or further assessment with the medical professionals onsite to assist with any medical queries that you may have. If you are unsure of your allergy history, the vaccination sites are able to securely access your allergy history if required.

Alternatively, you may consult your regular doctor for advice if you should receive the COVID-19 vaccination. Please note that any charges incurred for such pre-vaccination consultation with your doctor are not covered under the COVID-19 vaccination programme. Your doctor may provide a memo on your condition which will be useful for the medical team at the vaccination site to assess your suitability for vaccination. However, the final decision as to whether you should proceed with vaccination will be made by the medical professionals at the vaccination site.

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