Commentary: Inaccurate public understanding of COVID-19 vaccine efficacy has implications for vaccination rates
SINGAPORE: 18 months into the pandemic, we have multiple COVID-19 vaccines bachelor. This is cause for smashing optimism.
Scientific trials have shown that several have efficacies well above the minimum 50 per cent required past the World Health Organisation (WHO). Some, like the mRNA vaccines used in Singapore, have efficacies higher up 90 per cent.
The corporeality of information on these vaccines, yet, is likewise a source of confusion. Studies prove that, given the choice, people prefer vaccines with a higher vaccine efficacy number and fewer side effects. Media reports interpreting the latest findings from vaccine studies take understandably led the public to compare which vaccines are safer and which offering better protection.
Unfortunately, the scientific community has not communicated clearly what vaccine efficacy means. Therefore, there is misunderstanding about how much protection different vaccines provide and their implications for people deciding whether to get vaccinated.
To go an insight on how the public interprets vaccine efficacy, nosotros polled Facebook users in Singapore to see what they idea vaccine efficacy meant.
Only a quarter of users identified the accurate interpretation – if vaccine efficacy is 95 per cent, your chances of getting COVID-xix volition be 95 per cent lower if you are vaccinated than if you are non.
Instead, most people are under the impression that if you get vaccinated, you still have a 5 per cent chance of getting COVID-nineteen.
This suggests that many people have an inflated sense of their chance of COVID-19 if they go vaccinated, and this could undermine confidence in how much do good these vaccines provide.
READ: Commentary: Misinformation threatens Singapore'due south COVID-xix vaccination programme
This misinterpretation is understandable – what most people want to know is how probable they are to get COVID-nineteen if they get vaccinated.
Merely this is non exactly what vaccine efficacy measures. Your chances of getting COVID-19 depend not simply on how good the vaccine is, but too on how much virus is circulating in the population and other factors that affect your risk of COVID-xix.
These factors include your historic period, if yous have underlying medical conditions, if yous piece of work in a high-risk job, how much social interaction you have and your mask-wearing and hand hygiene practices.
Vaccine trials do not generally account for all of these social and lifestyle factors, so they provide express information about your private risk of contracting COVID-nineteen.
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WHAT VACCINE EFFICACY MEANS
We tin illustrate the thought of vaccine efficacy with an example from a scientific trial of the Pfizer-BioNTech vaccine, currently used in Singapore.
In that trial, around 36,000 people were randomly carve up into two groups. Half received ii doses of the vaccine, while the other half got 2 doses of an identical-looking but inactive placebo injection. Anybody was then observed for about half-dozen weeks to see who developed COVID-19.
In the eighteen,000-strong control group who received the placebo injection, at that place were 169 symptomatic COVID-19 cases over the six weeks. This equates to a risk of getting COVID-nineteen of about xc cases for every ten,000 unvaccinated people for this menstruum.
In contrast, in the 18,000 vaccinated individuals, there were only eight symptomatic COVID-19 cases, or about four cases for every 10,000 vaccinated people.
This means that among vaccinated people, the chances of getting symptomatic COVID-19 were about 20 times lower, or 5 per cent of the risk compared to people who got the placebo injection.
READ: Commentary: Why is COVID-xix surging in the earth's virtually vaccinated land?
Consequently, the vaccine has an efficacy of 95 per cent, because in vaccinated people it reduces the take a chance of getting symptomatic COVID-nineteen by 95 per cent compared to unvaccinated people. But it does not mean that 5 per cent of those who got the vaccine went on to go COVID-xix.
To date, the gamble of getting COVID-19 in Singapore has been very depression. Over 2020, before vaccination began, there were about two,400 community cases in a population of effectually v.4 million people living in the community. So for a resident in Singapore, the chances of getting COVID-nineteen in 2022 were near i in 2,250.
Had the Pfizer-BioNTech or Moderna vaccines been bachelor then, getting vaccinated would have reduced this take a chance by about 20 times, to effectually 1 in every fifty,000 vaccinated individuals.
Contempo increases in community cases hateful your risk of getting COVID-19 is currently somewhat higher, but getting vaccinated volition withal drastically reduce your chances of getting COVID-xix.
COMPARING EFFICACIES ACROSS VACCINES CHALLENGING
There has been much interest in which vaccines accept meliorate efficacy. Yet, comparing efficacy numbers for different vaccines is not straightforward.
Trials of unlike vaccines were done in different countries with varying levels of virus transmission, at different time points in the epidemic and with different virus variants circulating.
The trials were likewise done with different groups of volunteers – some included older adults, while others included generally younger people who tend to accept milder illness. And unlike trials diagnosed COVID-19 in slightly different ways.
All these influence the estimated efficacy. It is also important to note that headline vaccine efficacy numbers indicate the level of protection against any symptomatic COVID-19 disease.
READ: Commentary: Variants versus vaccines is becoming the new COVID-nineteen race
For the bulk of individuals, COVID-19 is relatively mild, and so it is more than of import to know how well these vaccines protect confronting severe illness.
The evidence so far is that nearly of the vaccines available are highly effective for preventing COVID-xix hospitalisation and death, even if some vaccines provide better protection against milder disease.
Agreement THE Apply OF ALTERNATIVE VACCINES
It is important to translate vaccine efficacy figures in relation to how much virus transmission is currently happening. The electric current depression levels of transmission put Singapore in an advantageous position.
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With rapid scaling up of vaccination, we tin drastically reduce the COVID-xix risk in the population and maintain information technology at a low level even as we ease other social distancing measures.
But for this to work, we need a very high uptake of vaccination in the population.
Recent surveys in March advise that a tertiary of adults are unwilling or nonetheless unsure nigh whether to get vaccinated. And so there is still work to practise to communicate the benefits of vaccination, address public concerns and reduce hesitation.
The Singapore Government is also taking other steps to improve the vaccination take-up rates.
They recently announced that the second dose of the Pfizer-BioNTech and Moderna vaccines, usually given inside three to 4 weeks, would be delayed to six to viii weeks. This volition allow more people to receive their starting time dose earlier.
Alternatives to mRNA vaccines will also be made available through the special access route. This will provide vaccination options for people who cannot receive the mRNA vaccines, including those with severe allergies.
READ: More than than xxx,000 people with history of anaphylaxis volition be invited to receive COVID-nineteen vaccine: Ong Ye Kung
With more options bachelor, people may wonder if it is prudent to mix and match vaccines, for instance, because of a belief that taking ii unlike vaccines gives better protection, or because of an unpleasant reaction to the first dose of a mRNA vaccine.
It is not recommended to mix and match vaccines unless medically advised, because we currently practise not have any information on how much protection this would provide. Different vaccines are designed and tested using specific dosing schedules and regimens.
Doses of culling vaccines, such as Sinovac, volition exist limited and it is of import that we reserve these for those who demand them for medical reasons.
(Are COVID-19 vaccines nonetheless effective against new variants? And could these increase the take a chance of reinfection? Experts explain why COVID-xix could get a "chronic problem" on CNA's Heart of the Matter podcast.)
QUESTIONS REGARDING VACCINATION TO BE TACKLED
The science of COVID-xix vaccines is indeed evolving constantly as we accumulate more information from large-scale vaccination programmes and the emergence of new variants.
For example, it is as well early to know how much protection these vaccines volition provide confronting more than recent variants, such as the Delta (B16172) variant currently causing global concern, or how long vaccine protection will last.
But vaccination remains overwhelmingly the all-time way to reduce your individual hazard of COVID-19. It is also currently the only viable way to navigate a safe relaxation of control measures while minimising the risk of big epidemics.
This is non to say that vaccination volition bulldoze out the virus completely. Every bit we open up our borders and ease restrictions, we need to accept that the risk of introducing the virus into the community will increase and cases will continue to occur.
Having a big fraction of the population vaccinated will vastly improve our chances of managing these clusters without spiralling epidemics overrunning our healthcare facilities, and without having to implement repeated lockdowns.
Dr Clarence Tam is an Assistant Professor at the Saw Swee Hock School of Public Health under the National University of Singapore.
Dr Hannah Clapham is an assistant professor at the same school.
Dr Yung Chee Fu is a senior infectious affliction consultant at KK Women's and Children'due south Hospital and an assistant professor at the Duke-NUS Medical Schoolhouse.
Source: https://cnalifestyle.channelnewsasia.com/commentary/commentary-inaccurate-public-understanding-covid-19-vaccine-efficacy-has-implications-vaccination-rates-285966
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