Syringes are prepared for doses of the Pfizer COVID-19 vaccine at a clinic in Los Angeles, California, on April 9.

A version of this story appeared in the April 14 edition of CNN’s Coronavirus: Fact vs. Fiction newsletter. Sign up here to receive the need-to-know headlines every weekday.

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The United States could have around 300 million excess Covid-19 shots by the end of July, health policy experts at Duke University estimated in a report Thursday, calling on the country to share doses more widely to address the stark inequality around global vaccine distribution.

The US has provided limited shipments of AstraZeneca’s vaccine – which is not yet authorized for use in the United States – to Mexico and Canada, but US Secretary of State Antony Blinken has said it won’t share shots more broadly until the country is “more confident” in its own supplies.

The US is the biggest financial donor to the global vaccine-sharing scheme COVAX, but the country has been tight-fisted with the actual vaccines it has in huge supply, while many others have none at all. Three-quarters of the world’s vaccines actually administered have been in just 10 nations, which together account for under half the world’s population.

“The world’s wealthiest nations have locked up much of the near-term supply. At the current rate vaccines are being administered, 92 of the world’s poorest countries won’t vaccinate 60% of their populations until 2023 or later,” wrote Dr. Krishna Udayakumar and Dr. Mark McClellan, health experts at Duke.

The report laid out a three-part plan in which the US should increase funding for COVAX, make excess doses available through the same scheme and create bilateral programs modeled on the President’s Emergency Plan for AIDS Relief – or PEPFAR – to provide shots and support to countries in need. It could also provide the support and materials for countries to produce safe and effective vaccines on their own.

The AstraZeneca vaccine, which the US has shared, has been paused in many age groups in Europe after regulators said the vaccine was possibly linked to dozens of rare but serious blood clotting events, some of them fatal. The US suspended use of the Johnson & Johnson vaccine on Tuesday after reports of the same rare clotting event in six people. The incidence remains extremely rare, at around one in a million.

Duke University’s estimate of 300 million excess doses had assumed the US would use J&J vaccine, but given the pause, their projections may be overstated. But it won’t change the big picture, as the J&J shot currently makes up less than 5% of around 190 million shots currently in the US.

YOU ASKED. WE ANSWERED.

Q. Officials are saying the J&J pause won’t slow down the US vaccine program. Is that true?

A. The pause in Johnson & Johnson’s Covid-19 vaccine rollout could have a significant impact on the US – but not in the way you might think. Practically speaking, the effect is likely to be minimal. Even if the suspension is prolonged, the US hasn’t relied very heavily on J&J’s vaccine, and the government said the US can meet its vaccination goals without the shot.

The bigger worry is that the J&J pause could deliver a serious psychological blow to confidence in vaccines generally. But it’s important to remember these events are extremely rare. Out of nearly 7 million people who’ve received the J&J vaccine, there have been reports of just six cases of people experiencing cerebral venous sinus thrombosis in combination with low levels of blood platelets, the US Centers for Disease Control and the US Food and Drug Administration announced Tuesday. One of those people died.

Dr. Arnold Monto, acting chair of an FDA vaccine advisory committee, wants to remind people that the other two vaccines being used in the US, made by Pfizer and Moderna, are designed differently, and have not been linked to this rare blood clot event that authorities are investigating in the J&J shot, as well as the AstraZeneca shot used widely in Europe. Here’s what else to know.

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WHAT’S IMPORTANT TODAY

Keeping middle seats empty on airplanes can significantly reduce Covid-19 exposure

Leaving the seats vacant on airplanes can reduce a passenger’s risk of being exposed to the coronavirus by 23% to 57%, according to a study published Wednesday by the US Centers for Disease Control and Prevention.

Researchers used laboratory models to simulate how much exposure to virus particles could be reduced when middle seats are kept vacant in an aircraft cabin. The models were based on the spread of bacteriophage aerosols used as a surrogate to estimate the airborne spread of the coronavirus. Bacteriophages are viruses that can infect bacteria.

The analysis did not measure the impact of wearing masks, which is currently required on flights, but the researchers noted that some virus aerosol can be emitted from an infectious masked passenger and so distancing could still be useful.

Denmark drops AstraZeneca from its vaccination program

Denmark is the first country in Europe to remove the AstraZeneca Covid-19 shot from its vaccination program, following announcements last week from medicines regulators in the European Union and UK confirming a possible link between the shot and rare but serious blood clotting events.

The UK has limited the use of the vaccine to people aged 30 and over, while other European nations have taken a more cautious approach, only offering the shot to people in much older age groups. Younger adults appear to be experiencing the blood clotting events in higher numbers. The European Medicines Agency (EMA), however, did not advise any change in the way the shot is used, saying the cases were very rare and that the benefits still outweigh the risks.

“We are basically in agreement with EMA’s assessment regarding the AstraZeneca vaccine,” said Søren Brostrøm, Director General of the Danish Health Authority, adding the shot wasn’t needed because the country had already reached “an advanced point” in its vaccine rollout.

“If Denmark were in a completely different situation and in the midst of a violent third outbreak, for example, and a healthcare system under pressure – and if we had not reached such an advanced point in our rollout of the vaccines – then I would not hesitate to use the vaccine, even if there were rare but severe complications associated with using it.”

1 in 5 Americans will ‘likely never’ choose to get a Covid-19 vaccine

The US, along with the rest of the world, is banking on widespread vaccination to dig itself out of the pandemic. But the latest numbers from a Monmouth University national poll about the vaccination suggest vaccine hesitancy will be a major hurdle to achieving that.

More than half of people polled (51%) reported that they already had at least one shot of the vaccine. Another 14% said they plan to get one of the vaccines as soon as they can. Another 12% said they are waiting and seeing whether to get the vaccine. But more than 1 in 5 Americans (21%) said they will “likely never” get the vaccine. Chris Cillizza breaks down what we know about this group of people, including what their political leanings have to do with it.

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