What are the potential side-effects from Covid vaccines?
All medications including vaccines have some side-effects. The most common with the Covid jabs are mild and short-lived, including localised soreness, fatigue or aches and headaches.
However the Oxford/AstraZeneca jab has been linked to a small but concerning number of reports of blood clots combined with low platelet counts (platelets are cell fragments in our blood that help it to clot).
These include a rare clot in the brain called cerebral venous sinus thrombosis (CVST). In an unvaccinated population, upper estimates suggest there may be 15 to 16 cases per million people per year. But also highly uncommon is the combination of CVST or other rare clots with low platelets, and sometimes unusual antibodies – and that combination is at the centre of current concerns.
The Medicines and Healthcare products Regulatory Agency (MHRA) said recipients of the Oxford/AstraZeneca jab should look out for new headaches, blurred vision, confusion or seizures that occur four days or more after vaccination.
The MHRA also flagged shortness of breath, chest pain, abdominal pain, leg swelling and unusual skin bruising as reasons to seek medical advice.
How many cases have there been?
Up to and including 31 March, the MHRA said it received 79 reports of cases of blood clots combined with low platelets, including 19 deaths, following more than 20m doses of the Oxford/AstraZeneca jab. That equates to about four cases for every million vaccinated individuals.
The MHRA says blood clots combined with low platelets can occur naturally in unvaccinated people as well as in those who have caught Covid, and that while evidence of a link with the Oxford/AstraZeneca vaccine has become stronger, more research is needed.
How may the vaccine cause these problems?
At present the mechanism by which the jab could cause clotting problems remains unclear. But experts have noticed a similarity to a clotting event sometimes seen among people given the blood-thinning drug heparin, whereby antibodies are generated that result in platelets becoming activated.
What is the current official recommendation?
The MHRA, along with the EMA and the World Health Organization (WHO), have all repeatedly said people should continue taking the Oxford/AstraZeneca shot because its benefits in preventing Covid infection far outweigh any risks.
The UK’s Joint Committee on Vaccination and Immunisation (JCVI) said it was recommending that people aged 18-29 should be offered other Covid vaccines – if available – provided they are healthy and at low risk of Covid.
Pregnant women should discuss with their doctors whether to have the Oxford/AstraZeneca jab as pregnancy can increase the risk of blood clots, the MHRA said.
Does the contraceptive pill increase women’s risk of blood clots more than the Oxford/AstraZeneca jab?
Combined hormonal contraceptives, which contain oestrogen, have been associated with an increased risk of blood clots including CVST, deep vein thrombosis and pulmonary embolism.
According to an EMA review in 2014, the risk of blood clots ranged from five to 12 cases per 10,000 women who take combined hormonal contraceptives for a year, compared with two cases each year per 10,000 women who are not using such contraceptives.
Should you have a second dose of the Oxford/AstraZeneca jab?
The vast majority of people who had a first dose of the jab, including under-30s, should get their second dose, with some exceptions.
“Anyone who experienced cerebral or other major blood clots occurring with low levels of platelets after their first vaccine dose of Covid-19 Vaccine AstraZeneca should not have their second dose,” the MHRA said. “Anyone who did not have these side-effects should come forward for their second dose when invited.”