People line up in Harare, Zimbabwe, to receive the Sinopharm vaccine on March 29, 2021.

A version of this story appeared in the April 16 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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It seemed nothing short of a miracle when it became clear that scientists had developed several effective vaccines against Covid-19 in less than a year. But announcements last week from European Union and British drug regulators finding a possible link between AstraZeneca’s Covid-19 shot and a rare blood clot condition have been a real low point in the pandemic.

A double blow for the global south, particularly Africa, is that it was just beginning to pivot toward the single-dose Johnson & Johnson vaccine when US medicines regulators paused its use on Tuesday, after just six cases of the same symptoms were reported among nearly 7 million people who’d had the shot. One of those cases was fatal. The company itself paused its rollout across Europe.

Several European nations had already limited the use of the AstraZeneca vaccine to older age groups after European medicines regulators found a “possible link” between the shot and the rare, sometimes fatal, blood condition. Denmark and Norway have dropped the shot altogether.

But many lower-income countries don’t have the same luxury to impose age limitations or hit the pause button after a handful of reports of blood clots, Nimi Princewill writes from Abuja, Nigeria. So many were relying on AstraZeneca as the one vaccine to help them dig their way out of the pandemic.

There are concerns now that a global two-tier vaccine system is emerging, with wealthy countries using the more expensive vaccines – like the Pfizer/BioNTech and Moderna shots – based on newer technology, while the cheaper AstraZeneca, and possibly the J&J, vaccines, are used in the global south. And that could hit confidence levels in Covid-19 in vaccines overall.

“If wealthy countries say they are only going to have ‘gold standard’ with the most expensive vaccines and then say AstraZeneca is not good enough for us in the global north, but it is good enough for the global south, it could reduce uptake of the vaccine and hamper efforts to vaccinate the world,” said Dr. Peter Drobac, Director of the Skoll Centre for Social Entrepreneurship at Oxford Saïd Business School.

YOU ASKED. WE ANSWERED.

Q. I’m a young adult, and these rare blood clot events seem to affect people my age. Should I still get the vaccine?

A. The US has put a pause on the use of the J&J vaccine while authorities work out if there is indeed a link. European and UK authorities think there is a possible link between the AstraZeneca vaccine and very rare blood clots in younger adults. Many European countries have limited the use of that shot to older adults, but it isn’t being used at all in the United States, where it isn’t yet approved.

But there are plenty of reasons why young, healthy people should get a Covid-19 vaccine. Young people may not be dying from Covid-19 in huge numbers, but they can get long-term complications from the disease. Plenty of young people are now “long-haulers,” suffering from issues like chronic fatigue, chest pain, shortness of breath and brain fog months after their infection. A recent study found that 30% of people who had Covid-19 still had symptoms up to nine months after infection.

Medical professionals are reporting an increase in the number of young people being hospitalized with Covid-19, including in ICUs. It’s unclear how much of a role new variants might be playing in this rising number, but in the US, doctors are reporting the B.1.1.7 variant, first identified in the UK, in many younger patients. Young people can also transmit the virus to more vulnerable people. Here’s what else to know about Covid-19 vaccines.

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WHAT’S IMPORTANT TODAY

New Zealand and Australia were Covid success stories. Why are they behind on vaccine rollouts?

The neighboring nations have been widely celebrated for their handling of the Covid-19 pandemic, both taking on a strategy to stamp out the virus altogether. They have been so successful that they have created a joint green zone, allowing people to fly between the two countries without undergoing the strict hotel quarantine period that has turned millions of travelers off visiting the countries over the past year.

But the tables are somewhat turning, Julia Hollingsworth writes, as the US and UK are leading the world in their mass vaccination campaigns, while Australia and New Zealand, as well as other Asia-Pacific nations, are lagging way behind. The situation differs for each country, but experts say one reason is where they are in the queue – these countries just didn’t sign agreements with manufacturers for vaccines as early as others. Some leaders are defending their slow rollout, saying there’s value in waiting to see how the vaccines work in other countries that need them more, but experts are urging them to speed up immunization or risk being left behind.

Pfizer says people are likely to need a third shot 6 to 12 months after their first round

Albert Bourla, Pfizer’s CEO, said that real-world data shows that protection drops with time but is still “extremely high” after six months in people who have been vaccinated, but that there will likely be a need for booster shots in the future.

It’s not yet clear exactly how often this would be needed, but Bourla said a likely scenario would be “for a third dose somewhere between six and 12 months and then from there, there will be an annual re-vaccination. But all this needs to be confirmed.”

Researchers at Stanford Medicine told CNN they have begun testing the Pfizer/BioNTech vaccine in children aged 2 to 5 in a Phase 1 trial of the shot. The group will trial the shot in 144 children across five sites in the United States, while Cincinnati Children’s Hospital began administering the shots in kids aged 2 to 4 on Monday, and plans to give the shot to some 340 children.

China’s economy grew by a record 18.3% in Q1 in bounce-back

China just reported its strongest quarterly growth in nearly three decades. The world’s second largest economy grew 18.3% in the first quarter of 2021 compared to a year earlier, according to government statistics released Friday. That’s the best quarterly growth since 1992, when China started publishing such figures.

The surge is mainly because of a low base effect, as China had shut down large swaths of its economy in early 2020 to contain the coronavirus outbreak. Still, the figures speak to a heathy recovery after a tumultuous year.

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Dr. Anthony Fauci, left, and Republican Rep. Jim Jordan sparred over whether Covid-19 restrictions violated Americans' civil liberties.

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