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  • Writer's pictureRahul Rao

Vaccine Hesitancy: A Nuanced Decision

by Rahul Rao, Varun Rao, and Yasir Aheer

The trajectory of COVID-19 has been dramatic to say the least, from the initial reports of cases in Wuhan in December 2019, to the massive spike in cases in the US last year, to the heartbreaking scenes in India early this year, and finally to the light at the end of the tunnel as vaccines have been rolled out over much of the globe (although not as much as required, as we have explored here). It appears that there is one dark chapter being written that threatens the happy ending of this novel - vaccine hesitancy.

The US is perhaps the most striking example of this. Having (nearly) successfully conducted one of the most ambitious vaccination plans across the world, with 370 million jabs having been administered as of September 1st, one would be forgiven for thinking its citizens were well and truly past the worst of it. However, yesterday Florida reported a 7 day average of above 20,000 daily cases - well above the peak of around 16,000 at the height of the January outbreak. Daily deaths are down to approximately 90, half of the 180 seen in January, but this is still a large number.

96% of the people hospitalised in Florida were reported to be unvaccinated. What is driving 35% of currently unvaccinated adult Floridians to refuse vaccination? A study by the University of South Florida in June 2021 found some of the biggest factors as described below:

Stated reasons for adult Floridians refusing a COVID-19 vaccine (June 2021, University of South Florida)

While some of these fears are ridiculous, the top three reasons are not particularly left-field and are linked. Efficacy and potential side effects are always concerns with medication and can only be measured through testing which has been rushed out of necessity, as we have explored previously on Our Few Cents. Despite the compressed timeline, the huge sample size is sufficient to provide some indication of their short term efficacy; the leading few vaccines are fantastically effective at preventing hospitalisations (>90%) but have somewhat differing capabilities in preventing symptomatic infection (88% for Pfizer vs 67% for AstraZeneca). This leaves side effects as the only valid concern.

Given the short developmental cycle of COVID-19 vaccines and the limited time-frame for testing, it is reasonable to ask what long-term side effects may occur. It stands to reason that any vaccine reactions that are developed over a period of years would not have had the chance to be detected this early. However, long-term side effects are incredibly rare in the history of vaccinations [1, 2, 3, 4]; side effects are predominantly observed within a few weeks after vaccination. Therefore, short-term side effects are of more concern and they vary widely depending on which vaccine is administered.

Both major mRNA viruses (Pfizer and Moderna) have a low incidence of inflammation of the heart muscle and surrounding tissue. The European Medicines Agency (EMA) found 283 such cases for 177 million doses of Pfizer and 38 for 20 million doses of Moderna. 5 people of advanced age or with pre-existing conditions died. The risk of contracting these symptoms is somewhere near 2 per million doses administered (roughly the chance of getting struck by lightning) and the fatality rate is 0.025 per million doses.

The EMA has also concluded that the Oxford-AstraZeneca vaccine has a rare incidence of life-threatening blood clots (thrombosis with thrombocytopenia syndrome, TTS). Studies of the cohort of vaccinated people in the UK suggest that the risk of developing TTS is somewhere near 15 per million first doses administered, with a fatality rate of 20%. With new knowledge, doctors at Alfred Health in Australia claim the clots are treatable and that 75% of Australians admitted to hospital with TTS have already been discharged in good health. Second doses are associated with a much smaller risk of clotting - about 1.5 per million.

In contrast to this is the chance of catching COVID-19 and the short-term and long-term impacts of a SARS-CoV2 infection. The probability of a SARS-CoV2 infection varies widely for the individual by geographical location, type of work, recreational activities, and social circle. For low-risk regions such as New Zealand or parts of Australia, the chances are near enough zero (although recent events may be changing this). For some high-risk regions such as Florida where over 20,000 of its 21.5 million inhabitants are catching COVID-19 every single day, the risks are significantly higher - on average, 1 in 1000 per day.

The short-term impact of COVID is clear to all. For many, there are no impacts - asymptomatic infection accounts for approximately 20% of all infections. These lucky few are also 42% less likely to transmit the infection to other people. For the remaining 80%, severity varies from typical infection symptoms (fever, chills) to classic respiratory symptoms (cough, shortness of breath) to gastrointestinal symptoms (diarrhoea, vomiting) to olfactory and taste disorders. These symptoms can put patients in hospital and on ventilators, fighting for their lives. The mortality rate for the original Alpha variant was 1.9%; Delta, though more infectious, is also less deadly at 0.3%. Still, 0.3% is nothing to be sniffed at - a person is approximately 1500 times more likely to die if infected with the Delta variant (assuming the original 20% mortality rate of TTS).

The long-term impacts are understandably not as well understood. So-called Long COVID comprises symptoms that continue for more than 12 weeks after infection and can affect even patients who presented with mild or asymptomatic cases of COVID-19. Long COVID symptoms include extreme fatigue, memory and concentration problems, joint pain, depression and anxiety, and sleeping difficulties, among a host of other conditions that massively affect quality of life. Somewhere between 10% and 25% of COVID-19 sufferers will get Long COVID. Frankly, Long COVID sounds every bit as horrific as COVID-19.

Given these depressing statistics, it behooves one to ask the question “Why would anybody refuse an approved vaccine they are offered?”. Despite the case presented for vaccines here, this is a nuanced decision for many people who have a choice of vaccines. For the rest of this article, we will focus on specifically our Australian audience to highlight the delicate balance that means reasonable people can fall to one side or the other of the current vaccine debate.

Australia currently has three vaccines on offer - Oxford-AstraZeneca, Pfizer, and Moderna. Our discussion will focus on the first two as Moderna is relatively recent to Australian shores. Any adult over 16 years of age is eligible for AstraZeneca, while the relative shortage of Pfizer means that it is prioritised for people in selected groups (healthcare professionals, quarantine workers and the like). ATAGI, the Australian Technical Advisory Group on Immunisation, recommends Pfizer for all adults under the age of 60 but recently amended their recommendation to approve the use of either Pfizer or AstraZeneca in an outbreak setting such as New South Wales.

For Australians above 60 years of age who have no imminent prospects of being offered Pfizer, the lower risk of TTS (approximately half that of adults under 50) with AstraZeneca and the increased severity of COVID-19 infection (see figure below) makes getting vaccinated a no-brainer.

COVID-19 case fatality rate broken down by age group (Our World In Data)

The cohort between 40 and 59 has had the choice of either vaccine for a few months now. This cohort is overwhelmingly choosing Pfizer for obvious reasons. Better efficacy and lower risk - what’s not to like?

For much of Australia’s population aged between 16 and 39, there is a difficult choice to make. On the one hand, the government’s promise of Pfizer eligibility for this cohort has been recently fulfilled. For a person in this age group, getting Pfizer today likely means being fully vaccinated with the advertised 88% protection by the middle of October. In contrast, the AstraZeneca vaccine requires a 12 week gap for maximum efficacy so even if taken today, the full protection of 67% would only be reached sometime in November. Shorter gaps are possible but result in lower efficacy. If the supply of Pfizer is adequate, waiting for Pfizer appears to be a quicker route to full vaccination.

That is, however, a big “if”. A lack of public confidence in the government’s vaccine rollout driven by the repeated revisions of previous targets means many young Australians are uncertain of getting access to Pfizer in the near future. Appointments for Pfizer have been cancelled due to weekly supplies not arriving and the NSW Health Minister Brad Hazzard has recently stated there is not enough Pfizer in NSW or Victoria to go around. Furthermore, both NSW and Victoria have extended the gap between Pfizer doses from the original 3 weeks to 6 to allow the limited supply to be used for more first doses. There is no guarantee that this won’t be extended further should supply shortages continue.

Until recently, it was believed Australia had bought itself time through its COVID-Zero strategy of 2020. This would have enabled every Australian to wait till sufficient supply of the vaccine of their choice was available. The current outbreak in NSW changes all that and it may be we never reach COVID-Zero again. Now how long can you afford to wait for the vaccine you want? The answer to that is highly personal and depends entirely on your risk of catching COVID, as alluded to earlier in this piece. Anybody, young or old, in NSW or Victoria where the virus is rampant is best off getting whatever vaccine they can right now to get full protection as quickly as possible.

In other regions such as Western Australia where SARS-CoV2 has been virtually eradicated and geographical borders make incursions rare, it is not unreasonable for young people to make the choice to wait for Pfizer.

Quite apart from the time-to-full vaccination are the questions of safety and efficacy. Clearly both vaccines are incredibly safe and effective but there is a small increase in the risk of debilitating side effects with AstraZeneca versus Pfizer, with that increase largest for the younger cohort.

Given the 88% vs 67% efficacy gap against symptomatic infection, the definition of “symptomatic infection” also plays a big role in deciding which vaccine to get. Does it include Long COVID? If so, 20% is a large gap. If “symptomatic infection” comprises only minor symptoms such as a fever and a cough, maybe 20% is negligible. Possibly it is still too early to have definitive answers to many questions on Long COVID.

One oft-repeated message is “the best vaccine is the one you can get right now”, but getting the vaccine available today might preclude you from getting a safer, more effective, and quicker-to-act vaccine tomorrow.

Parting thoughts

Vaccine hesitancy is the next big obstacle to eradicating SARS-CoV2 and is proving to be perhaps more difficult than developing the vaccine itself. Part of the reason vaccine hesitancy exists even amongst educated Australians who believe the science is that the two vaccines available have very different pros-and-cons lists and, for many, it is worth waiting for the vaccine they want. There is no doubt that we should all get vaccinated but when and with what is still a highly personal question.



Disclaimer: This article is based on our personal opinion and does not reflect or represent the views of any organisation that we might be associated with.


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