New studies trying to better understand the coronavirus and its effects have come in this week.
A large study in Denmark found that the vast majority of people who recover from Covid-19 remain shielded from the virus for at least six months, researchers reported on Wednesday. Reinfections can happen, but they are rare. The study suggests that immunity to a natural infection is unpredictable and uneven, and it underscores the importance of vaccinating everyone — especially older people, experts said.
“You can certainly not rely on a past infection as protecting you from being ill again, and possibly quite ill if you are in the elderly segment,” said Steen Ethelberg, an epidemiologist at Statens Serum Institut, Denmark’s public health agency.
Scientists have said that reinfections are likely to be asymptomatic or mild because the immune system will suppress the virus before it can do much damage. The researchers also did not assess the possibility of reinfection with newer variants of the virus.
New research has also begun studying the effects of the vaccine on patients with long-term Covid-19 symptoms. It is too soon to tell whether the shots have a broad beneficial effect on patients with continuing issues, sometimes known as “long-haulers,” but scientists are intrigued in the phenomenon after patients in the United States and Britain have reported alleviated symptoms after receiving the second dose of the vaccine.
a small study by British researchers that has not yet been peer reviewed found that eight months after people were hospitalized for Covid-19, those who were vaccinated experienced improvement in more long Covid symptoms than those who were not yet vaccinated. The 44 vaccinated patients in the study were older and had more underlying medical conditions, since people with those characteristics qualified for vaccines earlier.
Additional information comes from two surveys of several hundred people with long Covid symptoms, many of whom were never hospitalized for the disease.
Here’s what else we learned this week:
Who can get vaccinated and who cannot? Around the world, eligibility requirements vary drastically. Age is a defining requirement in most places, but income and connections can be far more important in others.
Prisons in the United States were hard hit by the coronavirus, but a state-by-state patchwork of vaccine rules has left prison inmates with different outlooks even as the Centers for Disease Control and Prevention has recommended prioritizing them.