A case of a 45-year-old PR who has already been vaccinated with 2 shots was infected with COVID-19, has caused concerns among members of the public in Singapore.
The PR’s parents had flown in from India on April 15. His father was diagnosed with COVID-19 on arrival and sent to hospital, while his mother was put under quarantine. The PR then sought permission to care for his mother at the quarantine facility and he was duly granted by the authorities to do so. Later, the PR was diagnosed with COVID-19 despite the fact that he had already been vaccinated.
Experts told the media that such post-vaccine infections, as well as reinfections for those who had been previously diagnosed with the disease, are to be expected.
Associate Professor Hsu Li Yang, an infectious diseases expert at NUS commented, “We expect an average of five out of 100 Pfizer- or Moderna-vaccinated persons to come down with symptomatic Covid-19 if exposed, and 10 per 100 vaccinated persons to come down with any Covid-19 infection (asymptomatic or symptomatic) based on the clinical trials and real-world data from Israel and the United States.”
He also said that viral mutations may also increase infections. In Singapore, the most commonly isolated variant in the past month is the B1617 “Indian” variant.
Professor Ooi Eng Eong of Duke-NUS Medical School said that most vaccines cannot “elicit immune response to levels sufficient to prevent infection”. But those who have received COVID-19 vaccines “around the world have also shown greatly reduced risk of hospitalization and death”.
“The evidence that vaccines work is now more and more abundant,” Prof Ooi emphasized. “Places with high vaccination rates, such as Israel, the United Kingdom and California, have all experienced sharp declines in Covid-19 cases. This is despite raging epidemics in these places at the start of the vaccination campaigns.”
Dr Asok Kurup, who chairs the Academy of Medicine’s Chapter of Infectious Disease Physicians and an infectious disease physician practising at the Mount Elizabeth Hospital questioned the efficacy of some vaccines given globally.
He said he has seen a few patients from India – the imported cases – who had received both doses of other types of Covid-19 vaccines “and yet developed full-blown disease with no antibody response”. But he added that the mRNA vaccines – like the Pfizer and Moderna ones used here – do protect against severe illness, and breakthrough infections are few and mild, or asymptomatic.
Wearing masks for the next couple of years
Professor Teo Yik Ying, dean of the NUS Saw Swee Hock School of Public Health, warned that infections among people who have been vaccinated will surface from time to time.
“Unless we can assess an individual’s immunity to infection, the likelihood that we will have to remain masked up for a long time more is a very real one,” he said.
Agreeing, Prof Hsu added that vaccines will not return us to a pre-Covid-19 era in the next couple of years, where people went mask-free and had the freedom to travel and congregate.
However, the upside of wearing masks and observing social distancing have resulted in large drops in cases of other diseases like the hand, foot and mouth disease and influenza, Prof Hsu noted. Singapore has not had a single laboratory-confirmed influenza case since May last year.