Every intervention has side effects, and COVID-19 vaccines are no different. In the trials of the Oxford/AstraZeneca vaccine, side effects such as injection-site pain, headache, fatigue, myalgia or fever were reported in more than one in ten people.
However, the likelihood of a serious adverse event with a COVID-19 vaccine is very small.
The latest data from the UK medicines regulator show that the overall reporting rate is around 3–6 yellow cards per 1,000 COVID-19 doses administered. And a yellow card report doesn’t necessarily mean that the adverse event is linked to the vaccine; it’s just when a link is suspected.
However, the recent announcement that younger people (18–29 year olds) should be offered an alternative to the Oxford/AstraZeneca vaccine, where available, owing to the risk of blood clots, may give more hesitant patients cause for alarm.
The Medicines and Healthcare products Regulatory Agency (MHRA) says that the evidence is firming up for a link between the Oxford/AstraZeneca and the occurrence of blood clots with lowered platelets (or thrombocytopenia).
Up to and including 31 March 2021, the MHRA had received 79 UK reports of blood clotting cases, with low levels of platelets, in patients who have had their first dose of the Oxford/AstraZeneca vaccine.
Of them, 19 died. This is after 20 million doses of the Oxford/AstraZeneca vaccine have been administered in the UK, equating to a risk of 4 in a million.
So why the caution? Of the 19 people who died, only three were under 30 years old. But the vaccine has not been given to many people in that age bracket and the risks versus the benefits are “finely balanced” in 20–29 year olds, said deputy chief medical officer Dr Jonathan Van-Tam at a press conference on 7 March 2021.
Government figures presented at the press conference show that the risk of serious harm owing to the Oxford/AstraZeneca vaccine is low for all groups — 1.1 per 100,000 in 20–29 year olds and 0.2 per 100,000 in 60–69 year olds if the levels of COVID-19 infection are low.
But the benefit that younger age groups gain from vaccination is much less; for example, they have a lower risk of being admitted to intensive care if they have COVID-19, compared with older age groups. However, the benefits begin to stack up the more the SARS-CoV-2 virus is circulating.
Overall, the decision to offer younger groups an alternative vaccine, and consider the risks in people of all ages at higher risk of a blood clot, appears a sensible precautionary move.
And it should not take away from the fact that all the approved COVID-19 vaccines are proving extraordinarily effective and have probably already saved thousands of lives.
However, it must be borne in mind that vaccines are unique — they are only taken when you are healthy and often to prevent serious disease in other people, as is largely the case in younger people when it comes to COVID-19.
There is a problem with vaccine hesitancy in some groups, and it is likely that some patients may be put off by this announcement.
But the public should be reassured by this move and not frightened by it. It shows a mature and independent pharmacovigilance system identifying risks, quantifying them and taking proportionate action to reduce them.
All healthcare professionals have a duty to give clear guidance to patients about the benefits and risks of an intervention, and in this case — for most people — the evidence is clear. The vaccine is safe. PJ
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