COVID-19 Vaccine and Booster: What You Need to Note

The information provided by Singapore Heart Foundation is for educational purposes only. It should not be substituted for professional health care. Please consult your doctor for professional advice.

(updated 18 Oct: Safety of booster shot for heart patients)

As of Oct 2021, more than 4.5 million people in Singapore have been fully vaccinated against COVID-19. If you are a heart patient and have not been vaccinated due to concerns about the safety and efficacy of the vaccine, you may have some of the following questions on your mind.

Here is a compilation of the questions asked by heart patients and answered by speaker Prof Tan Huay Cheem, Chairman of Singapore Heart Foundation; Senior Consultant, Department of Cardiology and Director, National University Heart Centre, Singapore.

Understanding the Vaccine

Would a vaccine made by conventional means, such as Sinovac, be a safer choice as compared to an mRNA type?

There is no evidence to suggest that one vaccine is superior to another at this point. I would say that you should go with the approved vaccines by Singapore’s Health Science Authority and not wait for the other vaccines to come along. As the other vaccines are still being evaluated, we are not totally sure about their safety and efficacy.

Is there any difference between the first and second doses? Why is there a higher reaction after the second dose?

The first dose is used to prime your body to the protein that is being released, so it has some kind of antibody. The second dose is a booster dose to remind the body of the “new” antibody that it needs to protect against, thus acting as stimulation to mount an even greater response. That is why some people develop more serious reactions.

Safety of Vaccine

Can a heart patient with a low heart rate of less than 50 or ejection fraction of less than 35 be vaccinated?

Yes. It is all the more important for patients with heart disease to be vaccinated as you have a higher risk of suffering complications from COVID-19. Anyone with heart failure or heart attack will be at tremendous risk if you catch the COVID-19 infection, as compared to people with no history of heart disease.

I am taking multiple medicines such as Perindopril, Bisoprolol, Aspirin. Can I still take the vaccine?

Yes, aspirin is not a contraindication, and these medicines are commonly prescribed to heart patients, particularly those with hypertension and blocked arteries. In fact, there are very few cardiac contraindications. So, no heart condition or specific drugs will affect your condition for vaccination unless you are allergic to the medicine.

I am allergic to aspirin; can I take the vaccination? My allergy will cause my whole face to swell.

Yes, you can still go for the vaccination. For now, we feel that allergy to aspirin is a different sort of allergic response from what we are worried about. So, you are still fit for vaccination.

My parents are in their 90s and have been advised not to take the vaccine, as they do not go out. Is this right?

I think it is even more important for them to be vaccinated as they form the high-risk population, which we want to protect from COVID-19.

While you may say they do not go out, but the family members or friends whom they are in contact with might carry the virus. And not only will carrying the virus put them in danger, but it will also expose everyone around them to it. So even if they do not die from the virus, there will still be social and economic costs (e.g. quarantined) incurred.

So I will say that, given the risks versus the benefit, the risk of getting vaccination is so low that it justifies the use of the vaccine in this case, even if they are 90 years old, particularly if they are still well and good. But if they are completely bed-ridden on a ventilator and so forth, perhaps there’s no point. If they are well and fit, please go for the vaccination.

I had recently completed a minor procedure that required general anaesthesia. How long should I wait before taking my vaccination?

As long as you have sufficiently recovered from the operation, you can go for it.

Other conditions suitable for the vaccine:

  • Amyloidosis skin problem
  • Asthma
  • Anxiety or depression
  • Any form of cardiovascular disease (e.g. aortic dissection, atrial fibrillation, history of cardiac arrest, hypertrophic cardiomyopathy, pacemaker, bypass or valve replacement)
  • Diabetes
  • Fibromyalgia with an allergy to steroid
  • Hepatitis B
  • High blood pressure (Hypertension)
  • History of nephrotic syndrome
  • Thyroid

Conditions to consult your doctor before you go for your vaccination:

  • Immune system disorder
  • Patients with a cancer history

Safety of Booster Shot

Is the COVID-19 vaccine booster safe for heart patients?

There is no contraindication to booster shots for heart patients unless there is an allergic or serious adverse reaction to the previous doses of vaccine. In that situation, you are advised to consult your doctor for a possible alternative vaccine.

Side effects of COVID-19 vaccine

What happens when an allergy occurs immediately after the first dose? Is the second dose really necessary?

I think if you develop allergic reactions, particularly in a very severe form, then automatically you’ll be disqualified from the second dose of vaccination. But if this is just a side effect, then it is not a problem.

In fact, if you have gone for your vaccination, you will realise that you have to be kept for observation for 30min. And this is because most of the severe allergic reaction occurs within the first 15 minutes. So, we are even more careful by extending the observation time to half an hour and if you don’t develop any reaction within that time, it’s unlikely that you will develop an allergy.

If there is swelling of lymph nodes at the neck area after vaccination, what does it say about the patient’s body reaction to the vaccine?

This is a reactogenic vaccine, as we call it, it provokes a reaction. Your body is mounting an immune response to it. The swelling of the lymph node is just part of the vaccination process and does not mean that you have caught the infection.

Some other symptoms will include headache or muscle ache. All you will need to do is take some painkillers and you should recover within the next two days.

If I develop symptoms like fever, rash, etc, should I go see a doctor or just take paracetamol?

You can take paracetamol because the fever and muscle ache is usually quite mild. However, if you don’t get better after a day, then perhaps you can consult your family physicians, but most people will recover by then.

What kind of allergy should I look out for after the first dosage to decide if I should proceed to take the second dose?

Anaphylaxis. That will usually occur within the first 15 minutes after vaccination. It will be monitored at the vaccination centre before you can go off.

What activities besides strenuous exercise should I avoid after the vaccination?

No specific activities. Just listen to your body. In fact, I went for my exercise the following day. But if you are feeling under the weather, just take a couple of days off work and rest at home.


Watch our health talk “COVID-19 Vaccine: Should Heart Patients Get Vaccinated?” here.

Read more about why heart patients should take the COVID-19 vaccine