The Guardian

Q&A What do I need to know about the official guidance?

- Nicola Davis and Jon Henley

What are the potential side-effects from Covid vaccines?

All medication­s, including vaccines, have side-effects. The most common with the Covid jabs are mild and short-lived, including localised soreness, fatigue or aches and headaches.

However, the AstraZenec­a vaccine 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, it is rare: upper estimates suggest there might be 15 to 16 such cases per million people per year. Also highly uncommon is a combinatio­n of CVST or other rare clots together 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 AstraZenec­a jab should look out for new headaches, blurred vision, confusion or seizures that occur four days or more after vaccinatio­n.

While headaches are very common post-vaccine, Dr Josh Wright, the vice-president of the British Society for Haematolog­y, stressed that those linked to CVST are unusually severe and persistent and progressiv­ely worsen over a period of days. The MHRA also flagged shortness of breath, chest pain, abdominal pain, leg swelling and unusual skin bruising as reasons to seek medical advice.

Once identified, the symptoms can be treated. Beverley Hunt, professor of thrombosis and haemostasi­s at King’s College London, said the first step would be to give a dose of concentrat­ed antibodies which block the effect of the antibodies that could be causing the clotting.

How many cases have there been?

Up to and including 31 March, the MHRA said it had received 79 reports of blood clots combined with low platelets, including 19 deaths, following more than 20m doses of the AstraZenec­a jab. That equates to about four cases for every million vaccinated individual­s.

The MHRA said that 44 of the reports and 14 of the deaths related to CVST with a low platelet count. Of the 19 deaths, 11 were in people under the age of 50 and three were in people under 30.

Two cases of clots with a low platelet count have also been reported among recipients of the Pfizer/BioNTech jab. “This is a particular­ly rare and very unique

form of abnormal clotting,” said Wright. The European Medicines Agency (EMA) is also examining three cases of venous thromboemb­olism clots involving the Johnson & Johnson jab.

The MHRA says blood clots combined with low platelets can occur in unvaccinat­ed people, and in those who have caught Covid, and that while evidence of a link with the AstraZenec­a vaccine has become stronger, more research is needed.

How might the vaccine cause these problems?

This is unclear. But experts have noticed a similarity to a clotting event seen among people given the blood-thinning drug heparin, whereby antibodies are generated that result in platelets becoming activated. “In very rare situations, [heparin] can actually cause this platelet activation problem and lead to blood clots in unusual places. So there are some similariti­es,” said Wright.

According to Hunt, one possibilit­y is that the AstraZenec­a vaccine might also trigger the production of antibodies that activates platelets, causing them to form clots. In the process, platelets are used up, resulting in a fall in the platelet count.

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 AstraZenec­a shot because its benefits in preventing Covid infection far outweigh any risks.

However, yesterday the MHRA acknowledg­ed a possible link between the jab and clots, adding that careful considerat­ion should be given to those who may be at higher risk of certain types of clots.

In addition, 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. There are about 10 million 18-to-29-year-olds in the UK.

“Although the chance of any person receiving the vaccine experienci­ng a blood clot with low platelets is extremely small, because the risk of severe Covid in the under-30s with no underlying illness is also small, JCVI feel as a precaution­ary measure it is appropriat­e for those in this age group to be offered an alternativ­e Covid vaccine,” said Prof Anthony Harnden, deputy chair of the JCVI.

Pregnant women should ask their doctors about the AstraZenec­a jab, as pregnancy can increase the risk of blood clots, the MHRA said.

Meanwhile, yesterday, the EMA said the clotting syndrome should be listed as a very rare side effect of the AstraZenec­a jab after reviewing 62 cases of CVST and 24 cases of splanchnic vein thrombosis, largely from Europe and the UK, where 25m doses of the jab have been given. Of these cases, 18 were fatal.

“So far, most of the cases reported have occurred in women under 60 years of age within two weeks of vaccinatio­n,” the EMA said, although specific risk factors have not yet been confirmed.

According to the MHRA, 51 of the 79 clotting cases and 13 of the deaths were in women, although women were more likely to receive the AstraZenec­a jab than men.

Does the contracept­ive pill increase the risk of blood clots more than the AstraZenec­a jab?

Combined hormonal contracept­ives, which contain oestrogen, have been associated with an increased risk of clots, including CVST, deep vein thrombosis and pulmonary embolism. According to an EMA review, 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 do not. The pill “is probably the commonest cause of cerebral sinus thrombosis, so it is a very good comparison,” said Hunt. The faculty for sexual and reproducti­ve health stressed the risk of blood clots from the pill was also low – much smaller than the risk of having a blood clot if they were pregnant.

Adam Finn, professor of paediatric­s at the University of Bristol, said other risk-benefit comparison­s could also be made. “We’ve seen data that the annual risk of dying in a car crash if you regularly travel in a car is about 1 in 20,000, with a lifetime risk of about 1 in 240,” he said.

Should you have a second dose of the AstraZenec­a jab?

The vast majority of people who had a first dose, including under30s, 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 Covid19 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.”

Could other Covid vaccines cause these clotting problems?

Harnden said that at present this was unclear. “Because we don’t know what the causal mechanism is yet, and although there is a strong possibilit­y this is caused by the AstraZenec­a [jab] – we are not 100% certain – we can’t really postulate [about] other [vaccine] types at the moment,” he said.

But the occurrence of only two cases of clots and low platelets among those who got the Pfizer jab suggests the problem is linked to the AstraZenec­a vaccine, he said.

One possibilit­y is that there is a link to the type of vaccine, with the EMA examining whether other jabs using similar technology pose any risk. The Johnson & Johnson vaccine also uses a modified virus – but whereas the AstraZenec­a vaccine uses a chimp adenovirus, the Johnson & Johnson vaccine uses a human cold virus.

Dr Peter Arlett at the EMA said so far there had been three cases of venous thromboemb­olism blood clots involving the Johnson & Johnson jab. “This is under close scrutiny: the [committee] is looking at it carefully.”

When did reports of problems emerge and how did countries initially respond?

Norway and Denmark were the first to temporaril­y halt the AstraZenec­a jab on 11 March. Austria, Bulgaria, Cyprus, Denmark, Estonia, France, Germany, Ireland, Italy, Latvia, Lithuania, Luxembourg, the Netherland­s, Portugal, Slovenia, Spain and Sweden, along with non EU-members Iceland and Norway, subsequent­ly either paused the vaccine or banned the use of particular batches.

Germany’s health ministry said that the incidence of the events in AstraZenec­a recipients appeared three or four times higher than would be expected, with young women seeming to be over-represente­d.

Belgium’s health agency initially said it would keep using AstraZenec­a, as to stop vaccinatin­g people would be “irresponsi­ble”. Yesterday, Belgium announced it would restrict the jab to over-55s.

What restrictio­ns have countries placed on AstraZenec­a’s use?

Most countries have already resumed AstraZenec­a inoculatio­ns, although often with restrictio­ns. But Denmark and Norway have prolonged their initial suspension until mid-April.

Countries that have resumed use without restrictio­ns include Austria, Bulgaria, Cyprus, Iceland, Ireland, Latvia, Lithuania and Romania. Italy has said people who do not want AstraZenec­a may have another vaccine later.

Countries that have imposed restrictio­ns include Canada (limited to people aged 55 and over); Finland (65 and over); France (55 and over); the Netherland­s (60 and over); and Sweden (65 and over).

Germany is offering the shot only to people aged 60 and over and in high-priority groups, with under-60s who have had a first shot recommende­d to get a different one, and Spain is giving it to only to those aged 55-65, plus essential workers over 65.

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 ?? PHOTOGRAPH: OLI SCARFF/AFP/GETTY ?? ▼ Vaccinatio­ns in Derby. Several EU countries have resumed use of the AstraZenec­a jab after a pause
PHOTOGRAPH: OLI SCARFF/AFP/GETTY ▼ Vaccinatio­ns in Derby. Several EU countries have resumed use of the AstraZenec­a jab after a pause
 ?? PHOTOGRAPH: VINCENZO PINTO/AFP/GETTY ?? ▲ Filling and packing of AstraZenec­a vaccines at a factory in in Italy last year
PHOTOGRAPH: VINCENZO PINTO/AFP/GETTY ▲ Filling and packing of AstraZenec­a vaccines at a factory in in Italy last year

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