Scientists have no answers to this latest Covid puzzle


There is a dearth of scientific studies with concrete answers, leaving policy makers and business leaders to formulate plans based on fragmented information. While some are renewing mask mandates or delaying the reopening of offices, others cite the lack of clarity to justify staying the course. It may all seem like a mess.

“We need to be humble about what we know and what we don’t know,” said Tom Frieden, former director of the Centers for Disease Control and Prevention and head of the nonprofit Resolve to Save Lives. little we can say for sure. The first is that it is a difficult question to resolve. “

In the absence of clear public health messages, people vaccinated do not know how to protect themselves. How vulnerable they are is a key variable not only for public health officials trying to determine, for example, when booster injections might be needed, but also to inform decisions about whether to reverse them. reopenings amid a new wave of viruses. On a smaller scale, the strangers left music lovers unsure whether it was okay to attend a concert and sparked a new round of discussions among parents wondering what school will be like.

Instead of answers, what emerged is a plethora of case studies providing somewhat different pictures of breakthrough infections. Variables, including when the surveys were conducted, the presence or absence of the delta variant, the proportion of the population vaccinated and even the weather at the time, make it difficult to compare the results and trend analysis. It is difficult to know which data could ultimately have more weight.

“It’s pretty clear that we have more breakthroughs now,” said Monica Gandhi, an infectious disease expert at the University of California, San Francisco. “We all know someone who has had it. But we don’t have good clinical data.”

One of the best-known outbreaks among those vaccinated has occurred in the small seaside town of Provincetown, Massachusetts, as thousands of vaccinated and unvaccinated people gathered on dance floors and at parties. home on the weekend of July 4 to celebrate the holidays – and what seemed like a turning point in the pandemic. About three-quarters of the 469 infections were in people who had been vaccinated.

Authors of a CDC case study said this could mean they were just as likely to transmit Covid-19 as the unvaccinated. Even so, they warned, as more people are vaccinated, it is natural that they also account for a larger share of Covid-19 infections and this study alone was not enough to draw any conclusions. The incident prompted the CDC to rescind a recommendation it had issued a few weeks earlier and once again urge those vaccinated to mask themselves in certain settings.

Yet the particular details of this cluster of cases may have made this outbreak particularly serious, according to Gandhi.

“The rate of mild symptomatic outbreaks in this population was higher due to a lot of indoor activity (including privacy), rain this weekend, little weather outside and heavy weather conditions. ‘a mix of people with different vaccine statuses,’ she said in an email.

A recently released and much larger CDC case study of infections in New York State found that the number of breakthrough infections had steadily increased since May, accounting for almost 4% of cases in mid-July. These researchers warned that factors such as easing public health restrictions and an increase in the highly contagious delta variant could impact the results.

Another case study from the CDC in Colorado found that the breakthrough infection rate in one county, Mesa, was significantly higher than the rest of the state, at 7% from around 5%. The report suggested that this may have been because the delta variant circulated more widely there, but also noted the age of the patients in Mesa and the lower vaccination rate may have played a role.

Research in Israel appears to support the idea that protection against serious illness wanes in the months following inoculation, and more recently, that groundbreaking cases could eventually lead to increased hospitalizations. Information is preliminary and cases of a serious breakout are still rare, but it reinforces the fact that some people will need booster shots in the months to come.

Case studies and data from some states in the United States have also shown an increase in breakthrough cases over time. But with the delta variant also on the rise, it’s hard to say whether the decrease in immunity to any type of coronavirus infection is to blame, or if vaccinations are particularly ineffective against the delta variant. It could be both, of course. Behavior change in those vaccinated could also be a factor, as they return to social gatherings and travel and dine indoors.

That said, some facts are well established at this point. Vaccinated people infected with the virus are much less likely to need to go to a hospital, much less likely to need an intubation, and much less likely to die from the disease. There is no doubt that vaccines offer important protection. But much of the nation – nearly 30% of American adults – have not been vaccinated, a fact that conspired with the highly contagious delta variant to push the country into another wave of epidemics.

“The big picture here is that vaccines are working and the reason for the rise in the United States is that we have too few vaccines,” Frieden said.

To some extent, breakthrough cases of any virus are expected. In clinical trials, no Covid vaccine was 100% effective – even the best vaccines never are. The more the virus is in circulation, the greater the risk of a breakthrough case. It is also common for some aspect of viral immunity to naturally wane over time.

At the moment, there are simply more questions than answers. Are breakthrough infections increasing due to the delta variant, waning immunity, or returning to normal life? Are people vaccinated more vulnerable to serious illness than previously thought? How common are breakthrough infections? It’s anyone’s guess.

“It’s generally the case that we have to make public health decisions based on imperfect data,” Frieden said. “But there’s just a lot we don’t know.”

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