BERLIN — As concerns grow over the highly contagious Delta variant of the coronavirus, Germany on Monday became the biggest Western country yet to announce that it will offer vaccine booster shots to a wide range of people considered potentially vulnerable, adding to growing momentum in rich nations to give additional shots to fully vaccinated people.
The move by Germany came even as a top European Union official criticized the bloc as falling far short of its promises to donate vaccine doses to Africa and Latin America. And with a limited global vaccine supply, health experts say the top priorities should be distributing doses to poor countries that lag far behind in inoculations, and persuading vaccine-resistant people in wealthy countries to get their first shots.
There is also still no consensus among scientists on the need for booster shots, but as fears rise of more pandemic waves and more costly lockdowns, a growing number of countries are preparing to give their people booster doses — or have already started.
Starting in September, Germany, Europe’s largest economy, wants to administer a booster of the Pfizer-BioNTech or Moderna vaccine to older people, residents of care homes, and people with compromised immune systems — and also to anyone who was already fully vaccinated with the two-dose AstraZeneca or single-dose Johnson & Johnson shots, which clinical trials have shown are not as highly protective.
“We will be prepared for the fall,” said Klaus Holetschek, the Bavarian health minister who made the announcement on behalf of all 16 German state health ministers. “I am convinced that a booster shot is important and right based on prevention alone. But I still hope science stays on the ball and generates even more reliable data to help us optimize our vaccination strategy.”
The issue of booster shots has been hotly debated in richer countries at a time when their rates of vaccination have been slowing. But as the Delta variant, which first ravaged India, has become dominant in much of the United States and Europe, and with cases surging again in June and July, more governments appear to be moving toward endorsing them.
Israel, an early leader in vaccination, began administering boosters to people 60 and older last week. A month ago, Russia made additional shots available to anyone six months after inoculation, and on Sunday, Hungary began offering them four months post-vaccination.
France is offering them only to those with weak immune systems, and plans to give them this fall to those who were the first to be vaccinated early this year — mostly people over 75 and those with serious health problems.
In Britain, which remains ahead of the European Union on vaccinations, health officials have been preparing to offer booster doses as early as September, but that plan has not yet been activated by the government. A committee of government advisers recommended in late June that everyone over 50 should be eligible but said the priority should be getting the shots to people over 70, health workers, nursing home residents, and younger adults with immune problems or other serious vulnerabilities.
The government advisers said that the plan would “maximize protection in those who are most vulnerable to serious Covid-19 ahead of the winter months,” when health officials fear that a coronavirus resurgence alongside other seasonal illnesses could put the British health system under strain once again.
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Several other European countries, including Italy and Spain, have said they will likely make boosters available to certain groups this fall. But none have indicated that they would go as far as Germany and include healthier and younger people who have had the shots from AstraZeneca or the one known in Europe under the Janssen Pharmaceuticals name, and in the United States as Johnson & Johnson.
In the United States, Biden administration health officials increasingly think that vulnerable populations may need additional shots even as research continues into how long the vaccines remain effective. Some people have already obtained boosters simply by not revealing previous vaccination.
But as governments, terrified of another surge in the virus, increasingly lean toward boosters, the need for them remains unclear.
Studies have indicated that immunity resulting from the Pfizer-BioNTech and Moderna vaccines is long-lasting, and researchers are still working to interpret recent Israeli data suggesting a decline in efficacy of the Pfizer-BioNTech vaccine months after inoculation.
Pfizer, which has begun making a case for booster shots in the United States, offered its own study last week showing a marginal decline in efficacy against symptomatic infection months after immunization, although the vaccine remains powerfully effective against severe disease and death.
Experts were divided on the utility of booster shots so soon after vaccination began. Experience with other diseases indicates that older people and those with weak immune systems might benefit, but there is little hard evidence with the coronavirus.
“The problem here is, we’re just sort of going on immunological priors, rather than really great data to justify things one way or the other,” said Deepta Bhattacharya, an immunologist at the University of Arizona. “I totally understand the decision, but I think we have to acknowledge that there’s a wide range of uncertainty on what it’s going to do.”
Booster doses may help some people with weak immune systems, but others may show little improvement even after a third dose, and still others may not need a booster at all, scientists say.
While dozens of mostly wealthy countries, including the United States and most of Europe, have administered more than 100 doses per 100 people, many other nations remain below five per 100 — primarily in Africa, where cases have soared as the Delta variant spreads.
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Doctors Without Borders said recently that it would be “unconscionable” to give booster doses in richer nations before people in poorer ones get their first doses.
“Wealthy governments shouldn’t be prioritizing giving third doses when much of the developing world hasn’t even yet had the chance to get their first Covid-19 shots,” Kate Elder, the senior vaccines policy adviser at Doctors Without Borders’ Access Campaign, said in a statement.
The new German guidelines, announced after the federal health minister, Jens Spahn, met with the state health ministers on Monday afternoon, cite “early study results which indicate that there can be an increased incidence of a reduced or quickly subsiding immune response after a full Covid-19 vaccination in certain groups of people,” notably those who because of age or pre-existing conditions have weakened immune systems.
The government did not give details of the studies underpinning Monday’s announcement and indirectly acknowledged the lack of conclusive data by urging scientists to do more studies to help improve vaccination strategies.
Under the German initiative, vaccination teams will be dispatched to care homes and other facilities for vulnerable people to administer shots of an mRNA vaccine like Pfizer-BioNTech and Moderna. Doctors and vaccination centers will be called on to provide the extra shots for other eligible people, including those who are young and healthy but have been fully inoculated with a so-called vector vaccine, like AstraZeneca or Johnson & Johnson.
It is the latest sign that governments are encouraging their citizens to mix and match vaccines in the hope of provoking a more protective immune response against Covid-19. Early results from a British vaccine study showed that volunteers produced high levels of antibodies and immune cells after getting one dose each of the Pfizer-BioNTech and AstraZeneca-Oxford shots.
The new German guidelines announced Monday also went a step further in encouraging parents to vaccinate children between 12 and 17, announcing that doctors and vaccination centers across the country would make the jab available to them before the start of the new school year.
Health ministers stopped short of making a formal recommendation for vaccinating children, but the move made plain their impatience with Germany’s Standing Committee on Vaccinations, which has so far refrained from guiding parents one way or the other, pending more data becoming available.
Vaccinating children “is one building block to allow a safe start into the new school year after the summer vacation,” Mr. Holetschek said.
Apoorva Mandavilli contributed reporting from New York, Benjamin Mueller from London, Aurelien Breeden from Paris, Gaia Pianigiani from Rome, Monika Pronczuk from Brussels, Raphael Minder from Madrid and Thomas Erdbrink from Amsterdam.