In Focus: Vaccinating Singapore, to combat Covid-19

By Amanda Lee, Writer, Communications and Outreach

Reports of a mysterious virus first surfaced in Wuhan city at the end of 2019. Little was known about it, and not many anticipated that this virus later known as Covid-19, would lead to be the world's biggest pandemic and crisis in recent times.

More than a year later, the world including Singapore, continues to battle this invisible enemy. Today, the coronavirus has claimed over two million deaths and infected beyond 93 million globally. But there seems to be light at the end of the tunnel.

In November last year, United States pharmaceutical giant Pfizer and German firm BioNTech became the first to develop a coronavirus vaccine, which showed successful data from a large-scale clinical trial.

On 21 December last year, Singapore became the first country in Asia to obtain the first shipment of the vaccine. The country is expecting more Covid-19 vaccine deliveries in the next few months, including those from US biotechnology firm Moderna and China's Sinovac.

So far (as of 15 February), at least 200,000 people – including Prime Minister Lee Hsien Loong, Health Minister Gan Kim Yong, and healthcare workers in public and private hospitals – have received their first doses of the Pfizer-BioNTech vaccine. The Covid-19 vaccine requires two injections, taken three weeks apart and experts say offers up to 95 per cent protection against the coronavirus.

The importance of Covid-19 vaccination

Since the early days of the pandemic, Singapore has implemented several safe management measures, contact tracing and testing. Despite having stringent measures in place to safeguard society, vaccination remains as one of the key strategies in the fight against Covid-19.

To reduce the chances of transmission and the number of people susceptible to the coronavirus, the Expert Committee on Covid-19 Vaccination has proposed to vaccinate the Singaporean population.

After independently reviewing clinical data on the safe and efficacy of the Pfizer-BioNTech Covid-19 vaccine, the Expert Committee assessed that it is suitable for those who are at least 16 years old. Vaccination is taking place progressively with priority given to persons at high risk of being infected by the virus, including healthcare and frontline workers, as well as those who are most vulnerable to severe disease and complications if they fall ill with Covid-19 (such as the elderly and persons with medical comorbidities).

However certain groups of people such as pregnant women, and immuno-compromised persons should not take the vaccine as there is insufficient data on the safety and efficacy of the vaccine for these groups of people.

To date, Singapore is rolling out the Pfizer-BioNTech vaccine, which is free for all Singaporeans, permanent residents, and long-term residents living in the country.  

Associate Professor of Health Services Outcomes Research Josip Car agrees that vaccination is an essential strategy in building a stronger population capacity to overcome the pandemic.

By strengthening an individual's immune resistance to the virus and minimising the chance of infection, the body is also better equipped to combat the virus if exposed to it, leading to a reduced severity of symptoms, he noted.

"In turn, it may be possible that person-to-person transmissions could be curbed with others benefitting from a lowered risk of infection as well. However, we would need further investigations on this prospect and the long-term impacts of vaccination within a community," said A/Prof Car.

Associate Professor Luo of Immunity and Infection Luo Dahai highlighted that when most of the population is immune to the disease, the spread of the virus is halted and these individuals as well as other unvaccinated people are less likely to be infected.

"This prevents COVID-19 infections from spiralling out of control and burdening healthcare systems," he added.

How Covid-19 vaccines work

Vaccines help the immune system to produce antibodies and traditionally comprise weakened or inactivated signature proteins of the virus. This includes the Covid-19 vaccines which must be stored at a cold temperature.

The Pfizer-BioNTech vaccine needs to be stored at -70 degree Celsius and lasts for only five days at standard refrigerator temperatures, while Moderna's vaccine must be stored at -20 degree Celsius and lasts for 30 days in a fridge.

In comparison, conventional vaccines such as Sinovac can be kept at normal fridge temperatures of 2 to 8 degree Celsius and could remain stable for up to three years.

Vaccines such as the ones from Moderna and Pfizer-BioNTech use messenger RNA (mRNA) to make viral proteins present on the outer surface of the coronavirus, said A/Prof Luo.

"The immune system learns to recognise viral antigen as a foreign invader and to then mount a defence against the actual virus later on. In this case, our bodies are not exposed to the actual virus but are trained and prepared to fight it."

On the other hand, conventional Covid-19 vaccines from Sinovac and Sinopharm make use of dead or weakened viruses while mRNA vaccines contain genetic instructions for our bodies to make the viral antigens.

"These vaccines retain the viral antigens and trigger the correct immune response without causing infection. You can think of vaccines as target practice for your immune system so that it recognises and attacks the virus when it comes along!" said A/Prof Luo.

Are Covid-19 vaccines safe?

Vaccines usually take a decade or more to be developed. With the Covid-19 vaccines approved in a short span of time, the public has raised concerns about its safety and efficacy.

However, Associate Professor of Human and Microbial Genetics Eric Yap explained that some of the vaccine development work done for SARS (Severe Acute Respiratory Syndrome) was carried over to the Covid-19 vaccine development. The Covid-19 virus, SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2) is a member of viruses called coronaviruses.

When it comes to Covid-19 mRNA vaccines such as the ones from Moderna and Pfizer-BioNTech, they make cells in the body produce a spike protein. This spike protein is found on the surface of the virus that caused the coronavirus.

A/Prof Yap, who is also the Principal Investigator of the Medical Genomics Laboratory, explained that the spike protein used in the mRNA vaccines to tackle Covid-19 is like the spike protein found in the SARS virus.

"A lot of work and cloning (were done during the research of) SARS, thus the early work done could be transferred over to Covid-19. So the work didn't start from zero. The science didn't start from zero. The technologies we see in the Covid-19 vaccines have been developed over many years, not necessarily for Covid-19 per se but subsequently applied to Covid-19," he added.

A/Prof Yap explained that vaccines and drugs undergo several phases of clinical trials, which are usually conducted one after another. "For Covid-19 vaccines to accelerate testing, the different phases of the clinical trials were done in parallel consecutively," he added.

Assistant Professor and Provost's Chair in Molecular Medicine Sanjay Chotirmall pointed out that the mRNA vaccines have been in research development for almost a decade. He added that there is a decade of science that goes behind the basis of some of these vaccines and that the approach was not started a year ago. 

"The science that started a year ago is focused on Covid-19, but the technology associated (with the vaccine) has been going on for more than a decade. What Covid-19 did was to accelerate its progress and apply to this new pathogen. Despite the need for something to curb the (spread of the) pandemic, there were no shortcuts taken in terms of clinical trials and they could be completed in record time because of the investment, global interest, and wide availability of individuals to recruit," said Asst Prof Sanjay.

Reportedly, the Pfizer-BioNTech vaccine has undergone clinical trials in more than 40,000 adults before scrutiny of the data and approval for use.

In Singapore, there have been four reported cases of anaphylaxis in people who received the first dose of the Pfizer-BioNTech vaccine.

The individuals in their 20s and 30s, developed rashes, breathlessness, lip swelling, throat tightness and giddiness. The symptoms were promptly detected and treated.

Three of them had a history of allergies, including allergic rhinitis and food allergy such as to shellfish, but none had a history of anaphylaxis which would have excluded them from receiving the vaccine.

Meanwhile, LKCMedicine Associate Professor Lim Poh Lian who is also the director of the High-Level Isolation Unit at the National Centre for Infectious Diseases said people who have mild allergic reactions, whether to food or medications, can get vaccinated.

"The severe allergic reactions we worry about and will not allow vaccination at this time include anaphylaxis and reactions that involve throat swelling. If you are unsure, please discuss with your doctor," she added.

A/Prof Car said millions of doses of Pfizer-BioNTech vaccine have already been given around the world. About 11 cases of allergic reactions including anaphylaxis per million doses were reported from the first nearly two million doses given in the US.

Of these, 71 per cent occurred within 15 minutes of vaccination, and no deaths from anaphylaxis were reported, said A/Prof Car.

Can the vaccines keep us safe from new strains of the virus?

The pandemic has swept across the world and saw some countries experiencing second or third waves. Countries remain on high alert, with many still imposing travel restrictions.

As every country battles coronavirus, three new variants of Covid-19 have surfaced in recent weeks: B.1.17 reported by the United Kingdom, 501.Y.V2 which has spread widely in South Africa and P.1 which was detected in northern Brazil.

They are said to be more contagious making it harder to stop the spread of the virus.

While there are vaccines to tackle the coronavirus, could they still protect us from the new variants?

A/Prof Yap said early data from Pfizer-BioNTech vaccine showed that it is still protective against new variants that are circulating widely in some countries. He highlighted that both the UK and South African variants contain a mutation within the spike protein known as N501Y mutation.

In vitro study data released by scientists from Pfizer and the University of Texas Medical Branch at Galveston in early January this year, showed the Pfizer-BioNTech vaccine induced antibodies that were effective on strains with the N501Y mutation.

However, A/Prof Yap pointed out that new virus lineages will continue to evolve after the vaccination programme is rolled out. Thus, there is a need for ongoing surveillance studies to detect them and evaluate if the current vaccines can protect against them. Nevertheless, he said there are more than 50 vaccines in production or undergoing trials – and they offer options if such variants escape a particular vaccine.

Meanwhile, in late January, Moderna said lab studies have shown that its Covid-19 vaccine would remain protective against variants of the coronavirus found in the UK and South Africa. However, the company will test a second booster of its vaccine.

Asst Prof Sanjay said while early data and analysis appears to show that the current Covid-19 vaccines confer protection against emerging variants, the natural history of viral behaviour means that more variants will likely emerge and current vaccines' effectiveness against them needs to be assessed.

"In most cases and in line with other past viruses, vaccines developed have remained effective. So, there is no reason to believe that SARS-CoV-2 would be different," he added.

Are we on our way to a pre-pandemic life?

As Covid-19 rages on, we are to remain vigilant. Although there are vaccines in place, we should not be hasty to lift all precautionary measures, said A/Prof Car.

Time is needed to develop and validate a safe and effective vaccination programme alongside an affirmative understanding to the extent of its protection against viral transmission, he noted.

"We have to accept our lives have taken a pivotal change since the emergence of Covid-19 and be receptive to global and local public measures in place to curtail its prevalence and repercussions. This is particularly important with plans for the gradual reopening of international borders."

A/Prof Luo said while vaccination will certainly help stop the spread of the virus, several questions remain about how long the immunity from the vaccine lasts or protects us from the emerging virus variants.

He cautioned, "It may be a long while before we're back to the old normal! As the pandemic continues, new strains of the virus may also emerge to be resistant to the vaccines. Nevertheless, a successful vaccination campaign will slow down the spread of the virus and prevent resistant strains from emerging. On that note, let's hope that no resistant virus strains appear in the future".