LONDON – Britain said on Wednesday it would reduce the use of the AstraZeneca vaccine in adults under 30 because of the risk of rare blood clots, a blow to the efforts of dozens of countries that depend on the vaccine to eradicate the disease. coronavirus pandemic in the midst of a global crisis arises in cases.
To increase concern, the European Medicines Agency outlined a “possible link” between the vaccine and rare clots, while stating that Covid-19 remained the far greater threat, leaving decisions on how to use the vaccine in the hands of the 27 Member States of the European Union.
Together, the decisions represented a considerable setback for the AstraZeneca shooting, which was seen as the main weapon in the battle to reduce deaths in the vaccine-hungry global south.
The most widely administered coronavirus vaccine in the world, it is much less expensive and easier to store than some of the alternatives, stimulating its use in at least 111 countries, rich and poor. Britain-based AstraZeneca has promised to deliver three billion doses this year, enough to inoculate nearly one in five people worldwide.
Britons under 30 will receive another vaccine, if one is available, with limited exceptions, officials said. Until Wednesday, Britain had not wavered in its use of the local vaccine, preventing many European neighbors from pausing injections because of unusual, although sometimes fatal, clots.
But cases began to appear in Britain as well, and since then there has been a consensus among global regulators that the evidence points to a plausible, yet unexplained link between the vaccine and rare clots.
Amid a violent wave of Covid-19 in Europe, security concerns have delayed inoculations, lowered confidence in the injection and created a patchwork of different policies across the continent. The most devastating effects of fear of security, however, can still befall the poorest nations that depend entirely on the AstraZeneca vaccine.
Concerns have arisen, although clots are extremely rare. On Sunday, officials said, European regulators received reports of 169 clots in the brain and 53 other clotting events, often combined with low platelets, among some 34 million people who received the AstraZeneca vaccine across Europe.
Britain has purchased enough vaccines from several manufacturers so that the change in AstraZeneca’s policy does not significantly slow the rate of inoculations. But other countries are starving for doses. Cameroon and the Democratic Republic of Congo have already postponed AstraZeneca vaccine injections amid growing concerns in Europe. Any further hesitation, the scientists said, could cost lives.
“In developing countries, the dynamic is to use the vaccine that you have or have nothing,” said Penny Ward, a visiting professor of pharmaceutical medicine at King’s College London. “In that case, the carnage follows.”
For the vast majority of people, British and European regulators said on Wednesday, the benefits of shooting AstraZeneca far outweigh the risks. Coagulation problems were appearing at a rate of about one in 100,000 recipients across Europe. Meanwhile, in Britain, the vaccine has reduced hospitalizations for Covid-19 – which in itself can cause serious clotting problems – and saved thousands of lives, regulators said.
British health officials estimated that the risk of being admitted to an intensive care unit for Covid-19 exceeded the dangers of unusual blood clots in almost all age groups and at almost all levels of outbreak.
But as younger people are less likely to develop severe Covid-19, regulators said, any vaccine administered in this age group must pass a higher safety barrier. British data also suggest that young people are more prone to rare clots, making health officials there and in Europe more cautious about how to give them the vaccine.
In response to the new regulatory guidance, Italy on Wednesday recommended not to give the AstraZeneca injection to people under the age of 60. Several countries, including Germany, France, Canada and the Netherlands, have already stopped using it on younger people, setting the age limit at 55 or 60. Norway and Denmark have completely stopped shooting while investigating.
“The balance between benefits and risks is very favorable for older people, but it is better balanced for younger people,” said Dr. June Raine, Britain’s leading drug regulator.
Blood clots have increased concern because of its unusual constellation of factors: blockages in the main veins, often those that drain blood from the brain, combined with low platelet counts.
The emergence of cases in early March presented countries with one of their most serious regulatory tests since the injections were first administered. When vaccinating millions of people, problems inevitably arose that were too rare to appear in clinical trials involving thousands.
But while scientists were pleading for coordinated action, health officials across Europe challenged the recommendations of the European Medicines Agency and suspended injections of the AstraZeneca vaccine. Most returned to the photos a few days later.
Some experts said the breaks were understandable, but the change was disorienting, especially in the midst of an ugly dispute between European lawmakers and AstraZeneca over drastic reductions in supplies that led some political leaders to falsely defame the vaccine. Research has begun to show that in Germany, France and Spain, most people doubted vaccine safety.
Overall, the use of the injection was hampered: across Europe, 64 percent of the administered doses of the AstraZeneca vaccine were injected into people’s arms, significantly lower than the rates of other injections.
“It was expected that there would be collaboration and more discussion between regulators, rather than many different countries moving in all directions,” said Professor Ward. “That aspect has really been the most useless.”
As doctors across Europe investigated the rare blood clots, they became more convinced of a link, though poorly understood, with the vaccine.
The inoculation appears to be triggering an immune reaction that targets platelets in a small number of people, doctors and regulators said. Platelets, in turn, were causing dangerous clots in different parts of the body, including the brain, leading in some cases to a rare type of stroke.
But it is not known why some people generated antibodies against platelets, doctors said. Some component of the vaccine, or an excessive immune reaction in certain containers – or both – may be the cause. No pre-existing conditions are known to make patients more vulnerable.
More women than men suffered from these clotting problems, but British regulators said this appeared to be the result of women being vaccinated in greater numbers because of first-line medical functions.
Regulators have asked vaccine users and doctors to watch for certain symptoms, including severe and persistent headaches and small bloodstains under the skin. Groups of doctors have released guidelines on how to treat the disorder.
As of March 22, regulators have carried out a detailed analysis of 86 cases, 18 of which were fatal, they said.
Concerns about the injection became acute enough in Britain this week that the University of Oxford, which developed the vaccine with AstraZeneca, stopped giving doses as part of a two-month trial in children.
“Safety has been our priority throughout the development of the vaccine,” said Andrew Pollard, the Oxford researcher responsible for the tests, on Wednesday. Clot identification, he added, “shows that the security system works.”
In the United States, AstraZeneca is preparing to apply for an emergency use authorization from the Food and Drug Administration. If and when they accept the request, the regulators of that agency must examine cases of coagulation.
The United States, filled with vaccines from three other manufacturers, may not need the injection of AstraZeneca. But any decision by the FDA must carry considerable weight in some of the poorest nations that depend on the shot.
The World Health Organization said a vaccine safety subcommittee met on Wednesday and noted that “rare adverse events after immunizations should be assessed against the risk of deaths from Covid-19 disease and the potential for vaccines to prevent infections ”. He said that a link to the clotting problems, although “plausible”, had not been confirmed.
For Britain, the AstraZeneca vaccine has become a major source of national pride and the backbone of the country’s rapid inoculation program.
Even if young people are at lower risk of severe Covid-19, scientists said, inoculating them remains essential to create sufficient protection in the population to end the pandemic.
Emma Bubola, Monika Pronczuk and Rebecca Robbins contributed to the report.