Enlarge / SOUTH TANGERANG, INDONESIA - JANUARY 7, 2021: A patient recovered from COVID-19 donate plasma at Indonesia Red Cross Transfusion Center in South Tangerang. (credit: Barcroft Media / Getty Images )

It's clear that the immune system can mount a robust response to SARS-CoV-2, as the vaccine trials have made clear. Beyond that, though, there are a lot of question marks. People exposed to the virus don't always produce much in the way of antibodies to it, and there have been a number of cases of reinfection. We're not sure how long immunity lasts or whether it correlates with antibody levels or something else–there hasn't even been great evidence that antibodies are helpful.

To give some sense of the challenge of sorting all of this out, we're going to look at three recently published papers that get at the interplay between the immune system and COVID-19. One finally provides some evidence that antibodies might be protective, another indicates that tamping down the inflammatory response might help, while the third suggests that immunosuppressives don't affect disease outcomes at all.

Antibodies good

Antibodies are a relatively easy way to track an immune response, and they've been used for that throughout the pandemic. But early studies found the number of antibodies produced in response to an infection varied dramatically between patients. There have also been clinical trials testing whether using antibodies obtained from those formerly infected could help treat those suffering from COVID-19 symptoms, with the FDA eventually granting this a controversial Emergency Use Authorization. President Trump also received an experimental treatment of mass produced SARS-CoV-2-specific antibodies.

Enlarge (credit: Eric Sonstroem / Flickr )

Did anyone have "mink farms" on their 2020 catastrophe bingo cards? It turns out that the SARS-CoV-2 virus readily spreads to mink, leading to outbreaks on mink farms in Europe and the United States . Denmark responded by culling its entire mink population, which naturally went wrong as mink bodies began resurfacing from their mass graves, forcing the country to rebury them . Because 2020 didn't seem apocalyptic enough.

More seriously, health authorities are carefully monitoring things like mink farms because the spread of the virus to our domesticated animals raises two risks. One is that the virus will be under different evolutionary selection in these animals, producing mutant strains that then pose different risks if they transfer back to humans. So far, fortunately, that seems not to be happening . The second risk is that these animals will provide a reservoir from which the virus can spread back to humans, circumventing pandemic control focused on human interactions.

Heightening those worries, mid-December saw a report that the US Department of Agriculture had found a wild mink near a mink farm that had picked up the virus, presumably from its domesticated peers. Fortunately, so far at least, the transfer to wild populations seems very limited.

Enlarge (credit: CDC.gov )

A variant of the pandemic coronavirus, SARS-CoV-2, is now dominating headlines and inspiring precautionary travel bans worldwide. But scientists are still trying to get a grip on what the variant can actually do differently and what it might mean for the nearly year-old pandemic.

Researchers in the United Kingdom—where the variant was identified and is now rapidly circulating—suggested it may be up to 70 percent more transmissible than other SARS-CoV-2 strains, stoking fear of surges-upon-surges of disease on the eve of year-end holidays. But other researchers are now rapidly working to collect data on the variant's interactions with human cells and immune responses to see if those interactions differ from those seen by other SARS-CoV-2 strains.

What we know

While much remains to be known about the variant, dubbed B.1.1.7, there are some reassuring aspects. For one thing, it's normal for viruses to accumulate the small genetic changes, such as those that created the new UK variant (more on that below). Many other variants have been identified throughout the pandemic, and none has spawned any nightmare scenarios.

Enlarge (credit: DeFodi Images )

Late Friday, the Food and Drug Administration issued an emergency authorization to a COVID-19 vaccine from a company called Moderna. The move follows an enthusiastic endorsement of the vaccine following an evaluation of clinical trial data by the FDA's Vaccines and Related Biological Products Advisory Committee. Moderna already has millions of doses prepared, and the federal government has pre-issued a large order for more, which will enable more extensive vaccinations than would be possible previously, where the agency had only issued an authorization to the Pfizer/BioNTech vaccine .

The authorization was considered to be a matter of time following the release of safety and efficacy data from a large clinical trial that had enrolled over 30,000 people. Emergency Use Authorizations require that a product or treatment meet a number of criteria, including the declaration of a medical emergency, which was done earlier this year, and the lack of an FDA approved alternative. (FDA approval is distinct from an Emergency Use Authorization, so the authorization of the Pfizer/BioNTech vaccine isn't a barrier to further authorizations.)

Beyond that, the product must be considered likely to be effective, and its potential benefits need to outweigh its potential risks. The votes from the members of the Vaccine Advisory Committee were unanimous that the benefits outweighed the risks, a conclusion that was well supported by the clinical trial data. That cleared the way for Friday's Authorization, which took place on a similar schedule to the authorization of the Pfizer/BioNTech vaccine the week prior.

Enlarge / Protests by medical staff took place both inside and out of the hospital. (credit: Ars Technica)

One of the more challenging aspects of the initial round of vaccinations is deciding who gets the first doses of a limited supply. The need to have a functional medical system in the face of an out-of-control pandemic has meant that most places have prioritized doctors and nurses who provide most face-to-face patient care. But an apparent failure to prioritize those caregivers at Stanford Medical Center has caused many of its doctors to stage protests today.

Ars received a copy of an open letter sent by the Chief Medical Residents to the Stanford administration that outlines the problems that sparked these protests.

In the US, a residency occurs after the completion of medical school, and is a requirement for the practice of medicine. Residents typically operate under the supervision of a physician in a training program at teaching hospitals, and they learn to practice a specialized branch of medicine, such as internal medicine or pediatrics. In many cases, residencies are followed by fellowships, which are used to develop further specializations. Because these positions are both temporary and required for practicing medicine, however, those occupying them have little political weight within hospitals.

Enlarge / This unassuming building in Massachusetts has taken on remarkable significance in recent weeks. (credit: JOSEPH PREZIOSO / Getty Images )

Earlier this week, the FDA released documents that summarized the data on a second SARS-CoV-2 vaccine candidate, this one from a company called Moderna. That document was the background for a meeting of the FDA's Vaccines and Related Biological Products Advisory Committee, which would consider whether the benefits of the vaccine outweigh its potential risks. That question is one of the key considerations for the agency as it decides whether to grant an emergency use authorization similar to the one it gave the Pfizer/BioNTech vaccine .

After an all-day meeting that frequently focused on other topics, the committee was near unanimous: 20 votes for approval, none against, and one abstention.

Emergency use authorizations have a number of requirements once a health emergency hsa been declared. There must be no alternatives that have achieved full FDA approval, there must be reasons to think that the treatment will be effective, and its benefits are considered likely to outweigh its risks. It's that final question—the risk vs. benefit balance—that the advisory committee was called to address.

Enlarge / Researchers have looked at whether there are genetic influences on who experiences a case of severe COVID-19. (credit: ALBERTO PIZZOLI / Getty Images )

The body's response to SARS-CoV-2 infection range from imperceptible to death, raising an obvious question: what makes the difference? If we could identify the factors that make COVID-19 so dangerous for some people, we could do our best to address these factors, and provide extra protections for those who are at highest risk. But aside from the obvious&dmash;health disparities associated with poverty and race seem to be at play here, too—we've had trouble identifying the factors that make a difference.

A recently published study takes a look at one potential influence: genetics. In a large study of UK COVID-19 patients, researchers have found a number of genes that appear to be associated with severe cases, most of them involved in immune function. But the results don't clarify how immune function is linked to the disease's progression.

All in the genes

The work took place in the UK, one of the countries involved in the GenOMICC ( Genetics Of Mortality In Critical Care ) project, which has already been exploring the genetics underlying hospitalization for communicable diseases. For the new study, the researchers worked with over 200 intensive care units in the UK to identify study participants. All told, they managed to get genetic data for over 2,700 critical COVID-19 patients. These were matched with people in the UK's Biobank who had similar demographics in order to provide a control population. The one weakness of this design is that some people in the Biobank may be susceptible to severe COVID-19 but simply haven't been infected yet, which would tend to weaken any genetic signals.

Enlarge / Richard Watkins,49, (in bed) is suffering from complications caused by Sickle cell disease. (credit: Washington Post/Getty Images )

Gene therapy has had a long and sometimes difficult history. Plenty of human genetic disorders can be traced to problems with a single gene, and that makes them a tempting target for correction. But someone died in a very early gene-therapy trial, which set the entire field back considerably. And, despite a far more cautious approach, the risks are still considerable, as two deaths during a trial occurred just this year .

But for researchers in the field, and those suffering from genetic diseases, this week provides some hope that the field's long-delayed promise might eventually be met. At a virtual scientific conference, a group presented the results of a large safety trial that saw 50 of 52 patients able to discontinue treatments for hemophilia. And a separate paper describes the use of CRISPR gene-editing and a blood stem cell transplant to successfully treat patients with sickle cell anemia or a related disorder.

Restoring clotting

The hemophilia trial was typical of most early efforts at gene therapy. In this case, the disease is caused by a defect in a single gene, so providing cells with a new copy will correct the problem. And, since the protein that's encoded by that gene circulates in the blood, you don't have to target a small and potentially difficult-to-access population of cells in order to correct things—targeting a new copy of the gene to any cells that can export proteins to the bloodstream will work.

Enlarge / If you can't socially distance, a face mask helps. (credit: Christopher Furlong / Getty Images )

Many countries that controlled their COVID-19 cases in the spring are now seeing rises in infections, raising the prospect that they'll face a second wave of cases, as many epidemiological models had predicted. But in the United States, the number of cases has never dropped to low levels. Instead, it varied between high levels of infection and very high peaks in cases. Why is everything so different in the states?

While there are plenty of possible reasons, a series of new studies essentially blame all the obvious ones: the United States ended social distancing rules too soon, never built up sufficient testing and contact-tracing capabilities, and hasn't adopted habits like mask use that might help substitute for its failures elsewhere. The fact that some of these studies used very different methods to arrive at similar conclusions suggests that those conclusions are likely to hold up as more studies come in.

Too soon

One of the studies, performed by a US-South African team, looked at the relaxation of social distancing rules in the US. Its authors created a list of restrictions for each state and the District of Columbia and tracked the number of COVID-19 deaths in each state for eight weeks prior to the rules being terminated. The number of deaths was used as a proxy for the total number of cases, as the erratic availability of tests made the true infection rate difficult to determine.