People should get flu jabs to protect themselves against concurrent infection of both Covid-19 and the flu, which can lead to severe disease, doctors have advised.
This is especially important as Singapore continues to ease travel restrictions and open its borders, they said, adding that influenza cases can be expected to rise.
With the new vaccinated travel lanes, more people here will be travelling abroad during the northern hemisphere winter that typically sees countries there experiencing a spike in flu cases.
In Singapore, safe management measures such as social distancing and mask wearing have been known to keep in check other unrelated respiratory virus infections, including influenza and the common cold.
This was proven in a research study conducted by doctors from Singapore General Hospital (SGH), KK Women's and Children's Hospital (KKH), and the Genome Institute of Singapore.
The study, published in scientific journal Jama Network on June 28, used data from more than 42,000 polymerase chain reaction tests for respiratory viruses across three public hospitals in 2019 and last year.
Dr Wan Wei Yee, the first author of the study, warned that Singapore travellers will find countries such as the United States and those in Europe having less stringent Covid-19 safe management measures, such as mask wearing and safe distancing not being mandated.
This could mean greater exposure to the flu, and bringing the virus back could put the elderly and more vulnerable people at risk of severe illness or even death, said Dr Wan, a senior consultant at SGH's Department of Microbiology. These risks could be mitigated if more people also get vaccinated against the flu, on top of getting a Covid-19 vaccine.
Dr Matthias G. Maiwald, a corresponding author of the study, noted a drop in respiratory virus cases from February to March last year, and during the circuit breaker period from April to June last year.
Singapore had raised its Disease Outbreak Response System Condition alert level to orange in February last year.
The drop could be due to the pandemic response measures - travel restrictions, social distancing, mask wearing and school closures, added Dr Maiwald, head and senior consultant in the Microbiology Service of KKH's Department of Pathology and Laboratory Medicine.
In comparison, Singapore saw a higher number of flu cases in December 2019 and January last year, which typically coincides with year-end spikes as people usually travel overseas, he said.
He noted that Singapore typically has two flu seasons - December to February and May to July - which coincide with the winter season in the northern and southern hemispheres, respectively.
Dr Esther Tan, a consultant at the Department of Respiratory and Critical Care Medicine of SGH, who was not involved in the study, said that based on studies done in the US and China, about 3 per cent to 10 per cent of Covid-19 patients also developed other viral infections, with the most common being influenza.
She added that getting a co-infection could be worrying for patients who have other long-term illnesses as this would mean increased chances of hospitalisation or death.
Dr Tan recommends getting a flu jab before the upcoming flu season at the end of the year. The jab should be taken 14 days before or after the Covid-19 vaccine.
