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CoronaCheck #60
In this week's CoronaCheck, we explain what, exactly, vaccine efficacy figures mean and take a look at the evidence for and against ivermectin as a COVID-19 treatment.
We also gather up fact checking from the US about proposed changes to the nation's voting laws, and outline some tips and tricks from Google on spotting online misinformation.
Vaccine efficacy versus effectiveness
For months, we've been hearing that COVID-19 vaccines are up to 95 per cent effective, but what does that figure actually represent?
First, it's important to understand the difference between vaccine efficacy and vaccine effectiveness, even though the terms are sometimes used interchangeably.
According to Gavi, a partnership between the World Health Organisation, UNICEF, the World Bank and the Bill and Melinda Gates Foundation which is co-leading the COVAX program to distribute COVID-19 vaccines in developing nations, "efficacy" refers to the degree to which a vaccine prevents disease in controlled circumstances such as a clinical trial, while effectiveness measures real-world results.
AAP
)"Although a vaccine that has high efficacy — such as Moderna's COVID-19 vaccine with 94.5 per cent efficacy and Pfizer's with 90 per cent efficacy — would be expected to be highly effective in the real world, it is unlikely to translate into the same effectiveness in practice," a Gavi statement reads.
Recent updates from Pfizer and AstraZeneca — the drug manufacturers responsible for the COVID-19 jabs available in Australia — suggest that the two vaccines have efficacy rates of 91.3 per cent and 76 per cent respectively, with real-world data compiled by Israel's Ministry of Health showing the Pfizer vaccine to be 97 per cent effective.
But what, exactly, are the vaccines effective at doing?
Pfizer itself measures vaccine efficacy in terms of how well the jab works to prevent "symptomatic disease, severe/critical disease and death".
As David Spiegelhalter, the chair of the Winton Centre for Risk and Evidence Communication at Cambridge University, and Anthony Masters, a statistical ambassador for the Royal Statistical Society, outlined in The Guardian, a 90 per cent efficacy rate does not mean an individual has a 10 per cent chance of contracting COVID-19.
"Imagine 100 people are ill with COVID-19," the experts explained. "‘Ninety per cent efficacy' means if only they'd had the vaccine, on average only 10 would have got ill.
"Vaccine efficacy is the relative reduction in the risk: whatever your risk was before, it is reduced by 90 per cent if you get vaccinated. There is a lot of confusion about this number: it does not mean there is a 10 per cent chance of getting COVID-19 if vaccinated — that chance will be massively lower than 10 per cent."
While that is likely to placate concerns around the toll of COVID-19 on health at an individual level, it doesn't mean that a healthy vaccinated person cannot spread the disease.
Experts interviewed by the ABC explained that efficacy figures refer to how good the vaccines are at preventing illness, rather than how good they are at stopping you from being infected with COVID-19 altogether.
"In clinical trials, the Pfizer vaccine was found to be 95 per cent effective at reducing disease," the ABC reported. "But whether it stopped people from getting infected in the first place isn't yet known — because it wasn't measured."
As Larisa Labzin, an immunologist at the University of Queensland, told the ABC, it is possible that people in Pfizer's clinical trials were infected with COVID-19 but did not develop symptoms.
These people would not have been identified or included in Pfizer's analysis, as the researchers only looked at whether the vaccine prevented or reduced the severity of COVID-19 symptoms.
AstraZeneca researchers, on the other hand, tested participants for COVID-19 regardless of whether they showed any symptoms, and found a 67 per cent reduction in infections after a single vaccine dose, according to an article in The Conversation written by experts from RMIT University.
There was also evidence that trial participants who tested positive despite receiving the AstraZeneca vaccine shed the virus over shorter periods of time.
"This data suggests the AstraZeneca vaccine also has potential to substantially affect virus transmission, by reducing the number of highly infectious people in a population," the RMIT researchers concluded.
The facts about ivermectin
Promoted ad nauseum as a potential COVID-19 cure by now-independent federal MP Craig Kelly, ivermectin, the active ingredient in medicines used to treat various parasitic infections, has not been recommended for use in treating COVID-19 outside of clinical trials in Australia.
According to Australia's medicines regulator, the Therapeutic Goods Administration, there is currently "insufficient evidence to support the safe and effective use of ivermectin… for the prevention or treatment of COVID-19".
US drug manufacturer Merck, which produces and distributes ivermectin, agrees, stating in a recent news release that there was "no scientific basis for a potential therapeutic effect against COVID-19 from pre-clinical studies".
Regardless, Mr Kelly's social media posts, including a post as recently as yesterday, suggest that a slew of scientific studies have found the drug to be an effective COVID-19 treatment.
So, what are the facts?
LoadingThe argument against ivermectin
Back in December, fact checkers at the Associated Press found there was no evidence ivermectin was a safe or effective treatment against COVID-19.
"Dr Amesh Adalja, an infectious disease expert at Johns Hopkins University, said most of the research around ivermectin at the moment is made up of anecdotes and studies that are not the gold standard in terms of how to use ivermectin," AP reported.
More recently, experts interviewed by AFP Fact Check agreed that more research was needed to determine the drug's efficacy.
"To be sure about the effectiveness of ivermectin, we need to conduct larger clinical trials, which we don't have at the moment," Nairobi-based epidemiologist Emanuel Okunga told AFP Fact Check.
Australia's COVID-19 Clinical Evidence Taskforce concurs, telling Fact Check in an email that current research "does not demonstrate the effectiveness of ivermectin in the treatment of COVID-19".
"Our assessment is that the certainty of the current evidence is low for mortality, invasive mechanical ventilation, adverse or serious events, discharge from hospital, admission to ICU and clinical improvement," a statement from the taskforce said.
"Certainty is very low for viral clearance, time to clinical recovery and duration of hospital stay."
Alex Grimm: Reuters
)This, the taskforce added, was due to "very serious imprecision" in the evidence available, including "reliance on a single study, limited number of patients, and/or wide confidence intervals".
"Given this uncertainty of benefit, and concerns of harms; we recommend that ivermectin only be provided in research trials, where there is the potential to generate further evidence on the effectiveness, or otherwise, of ivermectin."
The 'evidence' for ivermectin
One oft-cited study supposedly showing promising signs that ivermectin could be used to treat COVID-19 was published by Australian researchers in June 2020.
According to fact checkers at AP, the study showed that "ivermectin inhibited the replication of SARS-CoV-2 in a laboratory setting" but that was "not the same as testing the drug on humans or animals".
"Following the study, the [US Food and Drug Administration] released a letter out of concern warning consumers not to self-medicate with ivermectin products intended for animals."
Meanwhile, a separate study carried out by Bulgarian researchers found that while the results from the Australian study were replicable in humans, they would be reached "after massive overdose".
"It has to be emphasised that general public communication of drugs as potential COVID-19 therapeutics, based solely on in vitro data, is neither scientifically nor ethically appropriate," the Bulgarian researchers concluded.
"Ivermectin has been previously shown to exert antiviral activity in vitro against Dengue fever virus, influenza virus, West Nile Virus, Venezuelan equine encephalitis virus and heralded as a possible antiviral drug, but so far there has not been any clinical translation of these data."
In another (non-peer reviewed) study said to show ivermectin as an effective COVID-19 treatment, researchers who added small amounts of ivermectin to hydroxychloroquine and azithromycin found that it could lead to faster recovery times and shorter hospital stays.
The researchers noted, however, that "a larger prospective study with longer follow up may be needed to validate these results".
In its statement supplied to Fact Check, the National COVID-19 Clinical Evidence Taskforce noted that neither hydroxychloroquine nor azithromycin were approved COVID-19 treatments.
"The study is also not randomised, meaning there is significant potential for bias, and it is less likely to provide reliable information on the effectiveness of the intervention. As such, it is unlikely to provide useful information on the effectiveness or otherwise of ivermectin."
From Washington, D.C.
Voting laws have been the focus of heated debate across the US as the Senate considers the bill "H.R.1", known as the For The People Act. Should it be passed, the legislation would lead to wide-ranging changes to voter registration, absentee and in-person voting, and campaign finance rules.
Fact checkers at PolitFact have rounded up false and misleading claims about the bill, which passed the House of Representatives mostly along party lines (Democrats voted for the bill, Republicans were against).
PolitiFact found, for instance, that the bill did now allow for absentee ballots to be "mailed out to anyone without proof of the voter's identity".
"The bill would require states to send mail ballot applications to all registered voters before federal elections," the fact checkers noted, "but sending an application is not the same thing as sending an actual ballot, and these would go to registered voters only, whose identity and eligibility to vote are known."
Claims that the bill had provisions banning voters from needing to show ID at polling places was found to be partially false — in states where showing ID was a requirement, the bill would allow voters instead to present a sworn written statement attesting to their identity.
Meanwhile, a claim made by Republican congressman Ted Budd that H.R.1 would allow minors to vote was wrong. Rather, the bill would allow 16 year-olds to pre-register to vote when they turned 18.
Finally, a suggestion from former US vice-president Mike Pence that the bill would allow illegal immigrants to vote was false.
"The bill does not permit voting by non-citizens in US elections, whether they're in the country legally or not," PolitiFact said.
"Pence was referring to a provision that would require automatic voter registration for people using services at government agencies. But that section says government agencies would pass along a person's information for voter registration only if they are citizens.
"People would still be attesting that they are eligible to vote, with penalties for lying, and it would still be up to election officials to verify eligibility."
In other news: Tips for spotting misinformation online
Last Friday marked International Fact-Checking Day — falling perhaps aptly on April 2, following the onslaught of misinformation that comes with April Fools' Day.
In recognition of the day, Alexios Mantzarlis from the Google News Lab (and formerly of the International Fact-Checking Network, IFCN) offered up some handy tips and tricks for spotting online misinformation.
According to Mantzarlis, finding out more about the source of a piece of information can help with verification. He suggests searching for an alternative source by explicitly excluding the original web pages in order to get an unbiased opinion.
His next tip is to check whether images are being used in context by performing a reverse image search: "This will look for the picture to check if it has appeared online before, and in what context, so you can see if it has been altered from its original meaning."
Mantzarlis further suggests looking for news coverage to see how different news outlets have reported on a topic or event, or using Google's Fact Check Explorer to see what reputable fact checkers have had to say.
Edited by Ellen McCutchan
Got a fact that needs checking? Tweet us @ABCFactCheck or send us an email at factcheck@rmit.edu.au
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2021-04-08 22:56:56Z
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