Coronastream: vaccine warriors

Posted on April 13, 2021   by Dr Tim Inglis

In this special blog series, medical microbiologists led by Dr Tim Inglis summarise some of the research that will be essential to inform COVID-19 countermeasures. Find out more about the project in Dr Inglis' Editorial 'Logic in the time of coronavirus', published in the Journal of Medical Microbiology

It sounds like the grown-ups are arguing again. This time it's about the vaccine: orders, supply, distribution and delivery. The naming, blaming and shaming continues between states, nations, and nationstates while bemused citizens just want to know when they're going to get their first dose of the COVID vaccine.
Close to home we're taking it ever so cautiously, having pinned our hopes on a dream team combination of the Pfizer-BioNTech and AstraZeneca vaccines. Other vaccine candidates planned for use in Australia have yet to make it through the regulatory safety and efficacy reviews. At the time of writing, just over a million Australians have been vaccinated, with the first priority being quarantine workers, frontline health care staff and residents of aged care homes. Vaccination here is not mandatory, but there has still been some hesitancy, now fuelled by safety concerns about the AstraZeneca vaccine, on which the original vaccination timetable relied. Granted, a distinct lack of community COVID transmission allows a bit of time for caution, but our neighbours have a serious COVID burden and are struggling to cope without external help. Assisting Papua New Guinea, Timor Leste and possibly even Indonesia with our own vaccine manufacturing capacity makes good public health sense.
The vaccine jingoism (whatever happens, we have vaccine stock and they have not) coming from some corners of the world sells short the most vulnerable communities and fails to learn the first lesson of the current pandemic: we are all in this together. The standard this response will be judged by, is the sustained quality of the care and support we provide to the most inaccessible at-risk communities. We cannot afford to let pockets of unexposed populations go unprotected.
With this in mind, here are some recent publications on COVID vaccination:

Congruence: adverse events following immunisation

AstraZeneca’s COVID-19 vaccine: EMA finds possible link to very rare cases of unusual blood clots with low blood platelets

This report is worth reading in full to understand the context of the various responses from national pharmaceutical regulators, vaccine advisory panels and health departments. Responding to information on a new adverse event that may be caused by a vaccine, the European Medical Association's (EMA) Pharmacovigilance Risk Assessment Committee (PRAC) carried out a rapid review. This review was carried out in the context of a safety signal, under an accelerated timetable. A safety signal is information on a new or incompletely documented adverse event that is potentially caused by a medicine such as a vaccine and that warrants further investigation.

The adverse events in question are unusual clots, cerebral venous sinus, splanchnic vein and arterial thromboses. These are all unusual occurrences and have mostly been in women under 60 years of age, within two weeks of their first dose of the Vaxzevira (or AstraZeneca) vaccine. By 4 April 2021, 169 cases of cerebral venous sinus and 53 cases of splanchnic vein thromboses were reported among the 34 million vaccine recipients in the Eurpean Economic Area (EEA) and the UK. Thrombosis was associated with low platelets, or thrombocytopaenia, and is believed to have an immunological mechanism. This EMA release emphasises the rarity of these events, and that "the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects." As this rapid risk assessment does not confidently establish a cause-and-effect relationship, local responses to this announcement should be compared with the EMA's own headline summary: "EMA confirms overall benefit-risk remains positive."

Let's dig a little deeper and take a look at the risk-benefit trade-off:

Consistency: age-related harm-benefit trade-off from vaccination

Communicating the potential benefits and harms of the AstraZeneca COVID-19 vaccine

Using data from 1 April 2021, the Winton Centre compared the vaccine-related harms with estimated intensive care admissions for COVID-19, prevented by vaccination across three levels of COVID incidence (low, medium and high), over the age cohorts vaccinated in the UK. Noting that this study does not include anaphylaxis, which was too rare to analyse, and long-term sequelae (long COVID), the vaccine-associated harms exceeded benefits only at the lower end of the age range in a low incidence setting (for example, the UK in March). So, the UK has chosen to exclude adults under 30 years of age from AstraZeneca vaccination, preferring alternative vaccines instead. Taking this data and a near-zero community transmission rate into account, Australia has opted for a more cautious lower threshold of 50 years of age. A slow start to their own vaccination programme may be further hampered by these concerns, which will only be alleviated by publication of local vaccine adverse event data. Meanwhile, this release by the Winton Centre is an important step towards informing a confused general public, who are still waiting for their first vaccine dose.

Cumulative dissonance: vaccination intention and media use

Media usage predicts intention to be vaccinated against SARS-CoV-2 in the US and the UK

In this survey of media use and COVID vaccination intention in the United States and the UK, Allington and colleagues found that use of legacy media (print and broadcast) as a source of information, correlated with a higher intention to vaccinate while use of social media did not. Progressive voting preferences in both countries also correlated with higher vaccination intention, while younger age, female gender and lower educational attainment were associated with lower vaccination intention. The authors conclude that social media may not be as useful as once thought for promoting COVID public health messages.

Curtailment: choice of vaccine may improve willingness

The power of choice: Experimental evidence that freedom to choose a vaccine against COVID-19 improves willingness to be vaccinated
In this short letter, Sprengholz and colleagues studied the effect on vaccination willingness of restricted vaccine access. The study was conducted in February in Germany, where there is normally no choice of vaccine at the point of administration. Their findings provide evidence that restricting vaccine choice reduces willingness. There was no evidence that their study population had a higher preference for the Pfizer-BioNTech vaccine than the AstraZeneca vaccine, and in many cases, a choice of vaccine may not be feasible. They do, however, note that discussion of vaccine preference prior to administration may still be beneficial. As the study was reported before the European Medicines Agency safety notice on the AstraZeneca vaccine, it would be helpful to revisit the issue now.   



WHO Safe and effective COVID-19 vaccines

Global vaccine confidence trends infographic