SINGAPORE - Young adults with underlying health conditions such as obesity, heart disease, diabetes, high blood pressure and high cholesterol should get vaccinated against Covid-19, experts said.

This is to reduce their risk of severe illness and death if they get infected.

Those with such conditions are far more likely to get severely ill or die from Covid-19 even if they are young, compared with those who have no underlying conditions, said Professor Tan Huay Cheem, a senior consultant in the Department of Cardiology at the National University Heart Centre, Singapore.

"There is not a single cardiac condition that precludes vaccination here. It is the position of the Academy of Medicine and the Cardiac Society that every cardiac patient should be vaccinated because of the increased risk they would face if they catch a viral infection," he said.

"We know that the vaccine can cause myocarditis (heart inflammation), but it is actually a very rare condition.

"The vast majority of people with pre-existing cardiac conditions ought to have the vaccine to reduce their risk of getting the severe form of the infection, and they should do it as soon as possible."

Professor Teo Yik Ying, dean of the Saw Swee Hock School of Public Health at the National University of Singapore, said some young people may have chosen not to get vaccinated because they believe they will be fine even if they get infected, or they have underlying health problems and are worried the vaccine may make things worse.

But vaccination "makes a difference between life and death" and is even more important for those with such conditions, regardless of their age, he said.

"If you're someone like that, or if you know of someone like that, my advice is to speak to your family doctor, or the specialists that you're seeing for your conditions. Ask them directly: Can I take the vaccination or not? Seek professional medical advice, don't make the decision on your own."

The experts' comments come after two cases of Covid-19-related deaths involving a partially vaccinated 23-year-old Singaporean and an unvaccinated 34-year-old Singaporean were reported on Thursday night.

Both were said to have had multiple underlying conditions and are among the youngest patients who have died of Covid-19 complications in Singapore since the outbreak began last year.

The Ministry of Health said it could not provide further details on the two patients or their medical conditions due to confidentiality concerns.

Prof Tan said heart disease and other cardiovascular diseases are among the conditions most commonly associated with bad outcomes in Covid-19 patients.

He noted that Covid-19 is often thought of as a respiratory illness. The virus that causes it is named severe acute respiratory syndrome coronavirus 2 or Sars-CoV-2.

But it is also increasingly being recognised as a cardiopulmonary disease, meaning it affects the heart and lungs.

Prof Tan added: "While Covid-19 affects the airways and the lungs initially, the inflammatory response that sometimes happens can affect all the other organs as well, particularly the heart. We know that it has a very significant impact on people with heart disease."

The virus itself can attack heart muscles directly and cause myocardial injury in about a third of Covid-19 patients, Prof Tan said.

A patient's own immune system's inflammatory response to the virus can also cause heart attacks, heart failure, abnormal heart rhythm and clot formation, among other things.

Citing a study conducted in China's Wuhan city, where the virus was first reported, Prof Tan said a person with pre-existing heart disease and myocardial injury from Covid-19 had a 70 per cent risk of death, a tenfold increase compared with the 7 per cent risk for those without such a condition.

Asked if young people should be worried, given the news of the deaths, Prof Teo said the public should not fixate on the age of the two young patients who died of Covid-19.

"In general, people who are healthy and fully vaccinated don't need to fear Covid-19.

"If you have some medical conditions, it is even more important that you're fully vaccinated, and I think this advice holds true for people of all ages, not just young people."

Children under 12, including those with underlying conditions, are not currently eligible for vaccination.

Prof Tan said their parents and other household members should get themselves vaccinated to reduce the chance of infecting the child, and take the usual precautions such as safe distancing.

Severe infections in more young adults and even children are to be expected as the overall number of cases grows, Prof Tan added.

"When you have thousands of cases a day, surely it is going to affect some young patients once in a while, particularly those with pre-existing medical conditions.

"But by and large, this is still consistent with what we've been saying, that the disease affects the elderly a lot more than young people."