A piece by Sarah Zhang at The Atlantic (2/9/21) takes a pessimistic view of herd immunity ever being achieved in the U.S. The piece starts with an analogy for the concept, likening it to wet logs in a campfire. “If there’s enough immunity in a population — 'you can’t get the fire to start, period’,” Zhang writes, with the quote coming from an Emory University biologist. Zhang’s piece states that it becomes “downright impossible” to achieve herd immunity if vaccines only prevent serious COVID-19 rather than also preventing infection with SARS-CoV-2. And whereas the vaccines clearly do prevent serious illness, the evidence is still thin on whether the vaccines prevent infection. A more likely outcome, she writes, is that we never “cross the threshold of herd immunity,” and that the immunity of people who get vaccinated plus the immunity of people who overcome SARS-CoV-2 infections “dampen” COVID-19, so the disease comes to affect us like common colds, “which frequently reinfect people but rarely seriously.”

A more optimistic take appears in a 2/9/21 post by Katelyn Jetelina for her Your Local Epidemiologist newsletter. She estimates current U.S. herd immunity in the range of 12 to 30% (I’ve rounded figures), including those with antibodies from past COVID-19 infection and those who have received either one or both doses of an authorized vaccine. If you add to that the percentage of people who intend to get vaccinated, that puts us at 53% to 71% in the next several months, per arithmetic and some recent polls she cites. Some uncertain science lurks behind these figures, of course, and the variants add a wild card. As Jetelina writes, “I based today’s post on [a goal of] 70% herd immunity, but many scientists are now estimating that this is closer to 90% with the new variants.”

Katherine J. Wu at The Atlantic wrote a good piece that explains why “side effects” from COVID-19 vaccines are “just a sign that protection [from our immune system] is kicking in as it should,” as she puts it. She uses the example of her husband’s recent experience with the vaccine to tell the story (he’s a hospital neurologist, she writes). People are more likely to feel side effects from the second of the two doses of either the Pfizer or Moderna vaccines, per various reports. But that second exposure to the vaccine is crucial for strengthening our immune response to SARS-CoV-2 in the wild. “The body’s encore act, uncomfortable though it might be, is evidence that the immune system is solidifying its defenses against the virus,” Wu writes. She explains that our immune system starts to “lose steam” against invading substances, such as a vaccine, after a day or two. It takes several days for immune system weapons (T cells and B cells, and then antibodies) that can attack a foreign substance with “sniperlike molecules and cells” to kick in, she writes. That’s where the booster or 2nd dose of a two-dose vaccine comes in and finishes the job of preparing our immune system for exposures to SARS-CoV-2 (2/2/21).

A new video (2/11/21) at Scientific American explains the emergence of the new SARS-CoV-2 variants and why researchers are not certain that available vaccines will be as effective against all the variants. In the video, Sarah Cobey of the University of Chicago compares the emergence of the new SARS-CoV-2 variants to genetic mixing among flu viruses, a process that she loosely calls “viral sex.” This mixing occurs when two different influenza viruses infect the same cell and then swap and repackage parts to create new flu variants. With flu, that mixing means vaccine makers annually have to change the seasonal flu vaccine to make it more effective against new flu variants. The question is whether such changes will be necessary with the SARS-CoV-2 vaccines. A hopeful note in the piece: “Scientists say it will probably be years before the COVID-19 vaccine stops working if it ever does.” Reporting and editing by Sara Reardon; animation by Dominic Smith; editing by Jeffrey DelViscio.

A 2/3/21 opinion essay at STAT argues that “kids don’t need COVID-19 vaccines to return to school.” Dr. Vinay Prasad, a hematologist-oncologist  at the University of California, San Francisco, bases his opinion on some of the following: 1) kids are far less likely than adults to get COVID-19, particularly severe or fatal cases of it; 2) in most cases, outbreaks in communities are not being traced to infections at schools with strong distancing, masking and other safety measures in place; and 3) effectiveness and safety studies of COVID-19 vaccines for young children have not started, though some are underway older kids. When ready for evaluation by the U.S. Food and Drug Administration, COVID-19 vaccines for children should not be authorized on an emergency-basis, as COVID-19 vaccines have been for adults, Prasad states, in part because the disease is not a catastrophic disease among kids. The rate of harm for kids is more like that of the seasonal flu, he writes.

Some tips detailed in this 2/3/21 NPR piece by Maria Godoy for making your face mask more protective include: 1) double-masking, with a surgical mask under a cloth mask; 2) putting a filter such as two folded facial tissues in those two-layer masks that have pockets; 3) three-layer cloth masks; 4) using knots or hair clips to improve the fit of your mask; and 5) buying KN95 or KF94 masks, so we can keep more of the short-supply N95 medical-grade masks available for health care workers: 

You might enjoy “Things that are different in Europe,” by Sarah Hutto (1/25/21) in The New Yorker.