ZURICH, April 13- U.S. regulators have recommended pausing the use of Johnson Johnson's COVID-19 vaccine as they investigate rare blood clotting in six women, including one who died.
J& J also said it was delaying the rollout of its vaccine in Europe. U.S. officials said the temporary halt will only last a few days.
The move comes after Europe's drug regulator said it had found a possible link between AstraZeneca's COVID-19 vaccine and very rare blood clots in some adults who had received the shot.
Britain's Health regulator has recommended people under 30 get an alternative COVID 19 vaccine if possible, instead of the AstraZeneca shot.
Experts said the clotting risks for both vaccines remain highly rare and they are highly effective in providing protection against COVID 19, amid fears that reports of the rare side effects could deter people from getting their shots.
Here is what we know so far: With both the AstraZeneca and Johnson Johnson vaccines, the reports involve extremely rare clotting, including a type of blood clot called cerebral venous sinus thrombosis that were seen in combination with low levels of blood platelets, called thrombocytopenia.
A U.S. Food and Drug Administration committee plans to review the cases linked to the J& J vaccine.
Like their rare counterparts, the agencies described the clotting as extremely European.
As of 4 April, the European Medicines Agency has said that its side effects surveillance system had received 169 reports of CVST or clotting in blood vessels in the brain and 53 cases of splanchnic vein thrombosis or clotting in veins in the abdomen.
It is one out of 34 million AstraZeneca vaccine doses administered in Europe over the last three months in Britain and in Europe.
The Safety Committee of the EMA carried out a review of 62 cases of SVT and 24 cases of CVST, of which 18 were fatal.
The majority of cases occurred within two weeks of the person receiving their first dose.
German vaccination officials, who recorded 29 cases of CVST in women aged 20 to 59 who received the AstraZeneca vaccine, said the occurrence rate in that group was 20 times higher within 16 days of vaccination than expected.
Germany's health minister has said that 1 to 1.4 cases of CVST would have been expected during this time.
In J& J's case, all six recipients were women between the ages of 18 and 48, and the symptoms appeared six to 13 days after vaccination.
In total, more than 6.8 million doses of Johnson Johnson vaccine have been given in the United States through April 12. Similarly, most of the cases reported in Europe have occurred in women under 60, though this could be misleading since Germany and Britain say more women received AstraZeneca shots than men.
Most cases occurred within two weeks of people starting the AstraZeneca drug dosage.
What HAVE THE COMPANIES SAID?
J& J said it was working closely with regulators and noted that no clear causal relationship between the events and its shot had been established.
AstraZeneca said it was working to explain rare cases and possible mechanisms that could explain these extremely individual events.
What have the governments said?
The CDC is recommending using J& J's single-dose vaccine out of an abundance of caution to ensure that health care providers are aware of potential side effects and plan for proper management.
The MHRA approved an alternative vaccine to AstraZeneca for people under 30 following 79 cases of rare clotting coupled with low platelets, with 19 fatalities- 13 women and six men.
Eleven of the deaths were of people under the age of 50 and three were under the age of 30. In the United States, health officials said that the treatment of blood clots with possible ties to the J& J vaccine differs from what can be considered standard in such situations.
Usually, an anticoagulant drug called heparin is used to treat blood clots, they said.
In this environment, the administration of heparin can be dangerous and alternative treatments must be given. By contrast, Germany doctors and scientists investigating clotting associated with AstraZeneca shots have recommended that doctors give high concentrations of heparin, Fc receptor-blocking monoclonal antibody and intravenous immunoglobulin.
How were the regulation decisions affected?
In its findings, the EMA said on 18 March that on average, just 1.35 cases of CVST would normally have been recorded within 14 days of receiving AstraZeneca's vaccine, while 12 cases had been expected by the same date.
By comparison, four women out of 10,000 would get a blood clot from taking oral contraception.
British officials drew on statistics from the University of Cambridge's Winton Centre for Risk and Evidence Communication to explain their recommendations that older people get an alternative shot while young people can continue to get AstraZeneca's drugs.
According to the centre, the risk of serious harm is increased by vaccinations and the number of admissions to intensive care units falls sharply due to vaccinations, boosting the AstraZeneca shot's benefit-to-risk ratio.
The Centre concluded that only 0.4 people for every 100,000 in the 50-59 age group would experience vaccine-linked harm while 95.6 ICU admissions per 100,000 people would be prevented.
What is the EU doing to become more consistent and stronger?
The EMA, which said the benefits of AstraZeneca vaccine can outweigh any risks, said that rare blood clots with small blood platelets should be listed as very unusual side effects and countries should decide how to proceed.
These may vary from nation to nation, the EMA said, depending on factors such as infection rates and whether there are vaccine alternatives.
What is the theory of the games?
Among the likely causes of investigation are that the vaccine causes an unusual antibody in rare cases.
So far, risk factors such as gender or age have not been listed. In a paper published in the New England Journal of Medicine last week, the German scientists at Greifswald University concluded that the extremely rare cases of clotting with low platelets- something they are calling vaccine-induced immune thrombocytopenia- are triggered by antibodies found in the affected patients after vaccination with AstraZeneca shot.
A separate group of Norwegian scientists have made similar conclusions- that AstraZeneca's vaccine triggered an immune response that could have led to clotting in a small number of people- in their own article, which has also been published in the New England Journal of Medicine.
Like the EMA, Andreas Greinacher, an expert on drug-induced immune responses, is seeking clues about why in rare cases people developed clots and low platelets after getting the vaccine, while the vast majority did not.