SINGAPORE: Last week, Pfizer announced early results from its COVID-19 mRNA vaccine, which suggested that it could reduce the risk of COVID-19 by 90 per cent.
This was followed earlier this week by a similar announcement from US-based Moderna about their own vaccine, also based on mRNA technology.
Effective COVID-19 vaccines are key to our ability to control the pandemic and resume travel and economic activities without the need for repeated lockdowns.
Therefore, news indicating that it is possible to develop highly effective vaccines against COVID-19 is very welcome, as this has historically not been the case for other respiratory viral infections, such as influenza.
Final trial results are expected in the coming weeks and still have to be reviewed by the wider scientific community. Beyond these initial promising results, however, there are scientific and practical reasons to be cautiously optimistic about the implications for ending the pandemic.
HOW WILL VACCINES WORK?
The scientific issues are well-recognised and will take time to unpack. At present we do not know how well the vaccine works in specific groups of people.
This is important, because we know that the elderly and those with underlying medical conditions are at higher risk of severe illness, but vaccines typically work less well in these groups.
We also need to have a better understanding of how these, and other COVID-19 vaccines being developed, actually work from an epidemiological perspective.
For example, if a vaccine stops infected people from getting COVID-19 symptoms, but does not actually prevent them from being infected in the first place, this means that vaccinated individuals could still pass on infection to others.
If this is the case, the vaccine will help to prevent severe illnesses and reduce strain on healthcare systems, but will not be sufficient by itself to get rid of the virus from the population.
Finally, we need to know how long these vaccines provide protection for and ensure that they do not result in serious and unacceptable side-effects in the long-term. This will require careful studies in vaccinated populations over several months and years.
What we learn from these studies will be crucial for informing vaccination strategies in the coming years to maximise the benefit from these vaccines.
For example, it will tell us whether a single course of vaccination is sufficient to provide long-term protection, or whether repeated vaccinations are needed at regular intervals.
It will also give us valuable information about what fraction of the population needs to be vaccinated in order to reach the crucial herd immunity threshold - the point at which enough people are protected to bring epidemics under control and prevent future resurgences.
CHALLENGES ON A MASS SCALE
In the short to medium-term, however, the priority should be to deploy these vaccines as quickly as possible to where they are most needed. Uncertainty over these scientific issues should not stop us from forging ahead with plans to introduce vaccines that are deemed safe and efficacious in clinical trials.
The more quickly we introduce these vaccines, the more we will learn about how best to use them.
Introducing these vaccines on a mass scale is in itself a formidable challenge. The Pfizer vaccine is at the most advanced stage and around 300 million doses are expected to be available for use next year. This is still far short of what is needed to control the pandemic globally.
To be effective, the Pfizer vaccine also needs to be stored at a temperature of -70 degrees Celsius, much colder than commonly used vaccines.
Distributing the vaccine thus requires building infrastructure to maintain the cold chain, which will be particularly challenging in remote areas with unreliable electricity supplies.
MULTIPLE VACCINES BRING OTHER ISSUES
Fortunately, there are a number of other promising vaccines in the pipeline based on alternative approaches that may pose fewer logistical challenges. The Moderna vaccine, for example, is based on similar mRNA technology, but has been formulated in a way that allows it to be stored in a standard freezer.
Having multiple vaccines available increases our chances of protecting a sufficiently large fraction of the population in order to control the pandemic. But getting these vaccines to people on the mass scale needed to achieve this comes with difficulties.
Most countries do not have registries to record vaccinations in adults, as they do for children. Such registries are important to track how many people have been vaccinated in the population, and how many doses they have received.
They can also provide important information to monitor changes in vaccine effectiveness over time.
If multiple COVID-19 vaccines are introduced, these registries become all the more important to monitor how well each vaccine is performing. Countries thus need to invest in the infrastructure to develop and maintain these registries, which comes at additional cost.
Initially, vaccine supplies will be limited, and countries will have to make difficult choices about who to prioritise for vaccination.
If there are not enough vaccine doses to go around, should we give priority to those at highest risk of severe illness, or to healthcare staff and other essential workers who are at higher risk of being infected and infecting vulnerable patients, or to those who can most contribute to economic and social recovery?
And how do we use vaccination in combination with other control measures? If individuals are vaccinated, should they immediately face less stringent movement and control restrictions?
ENSURING EQUALITY AND FAIRNESS
Ethically, it may be reasonable to ease restrictions on those who pose lower risk. But if vaccine supplies are limited and some groups are given priority, it may mean that these groups also preferentially benefit from greater freedom to travel or undertake activities that bring social and financial gains.
Public perception of such policies needs to be considered carefully to avoid backlash, and countries may need to put in place measures to reduce the impact on those who are unable to benefit initially from vaccination.
As members of a global community, we should also be concerned about ensuring that these vaccines are allocated fairly so that all countries can share equitably in the benefits and not just those who can most afford to pay.
To this end the World Health Organization, together with The Vaccine Alliance (Gavi) and the Coalition for Epidemic Preparedness Innovations (CEPI), has spearheaded the global COVAX initiative, supported by many countries including Singapore, to ensure that a fraction of vaccine stocks are made available to low-income countries at affordable prices.
But what does a fair system for global vaccine allocation look like? Should we prioritise the countries worst affected by COVID-19 related deaths and related control measures? Or countries in which socio-economic recovery will be hardest without vaccine access? And how should we measure these criteria? These are questions with no easy answers.
MANAGING EXPECTATIONS AND COMMUNICATING RATIONALE
Finally, communicating the rationale behind vaccination policies effectively with the public will be crucial.
If vaccine supplies are limited, some groups in the population will need to wait longer to get access to vaccines.
It may also be necessary to use different types of vaccine in different groups of people. For example, some vaccines may provide better protection than others for people at high risk of severe illness, such as the elderly.
In addition, some countries may consider making vaccination compulsory in certain groups, such as healthcare workers or those caring for vulnerable people.
The public will need to understand why these policies are in place and be assured that they are not being denied the benefits of vaccination or being offered an “inferior” product.
Rumours and misinformation about the safety of COVID-19 vaccines, and their impact on public acceptance of vaccines, are already becoming a concern in many countries.
In Singapore, recent surveys indicated that 20-30 per cent of respondents would not be willing to take a COVID-19 vaccine even if it was known to be safe and effective.
Maintaining high confidence in vaccines and countering the spread of misinformation will be key to ensuring we can achieve levels of vaccination sufficient to bring the pandemic under control.
The availability of multiple promising COVID-19 vaccines less than a year into this pandemic is a testament to our ability to tackle global challenges through science, innovation and political will.
But we should be mindful that vaccines are not a magic bullet. On the long road to recovery, we are only at the beginning.
Dr Clarence Tam is an Assistant Professor at the Saw Swee Hock School of Public Health under the National University of Singapore. Dr Voo Teck Chuan is Assistant Professor at the NUS Centre for Biomedical Ethics, Yong Loo Lin School of Medicine.