(UPDATE 9/6/21: now that more is known about the Delta variant, I'm being more conservative than I articulated below, and managing to a weekly risk budget of 400 microcovids. The main difference beyond what I articulated below is that I'm no longer interacting freely with fully vaccinated people, but rather considering how risky various interactions are and moderating those accordingly or masking/distancing. I may relax that again based on my determination of how big an issue long covid is, which I'm exploring here: https://www.lesswrong.com/posts/jfHZR6Ykmc5DBSLCp/cliffs-notes-how-much-should-fully-vaccinated-people-care)

ORIGINAL POST, FOR REFERENCE:

As someone who is now several months past my second dose of Pfizer, and who lives in San Francisco, which opened up completely earlier this month, I've been debating what events / spaces are still too risky to spend time in. Here are the rules of thumb I've been following and the thinking that informed them; would be interested in input!

I imagine I could make further progress with further thinking (and/or maybe I should just pick a risk budget and use the microCOVID calculator to stick to it), but figured that since I've done this amount of research and thinking, it might be helpful to some and low-cost for others to help fill in some gaps.

Summary:

• I am ok interacting freely (unmasked, indoors) with fully vaccinated people
• In "mixed" environments (where I could be interacting with unvaccinated people), I will still take precautions:
  • Outdoors: wear a mask (KN95 or better) OR distance
  • Indoors: wear a mask (KN95 or better) AND distance
• I will avoid events / spaces where those precautions are impossible
• Open questions: 
  • How risky is it to loosen precautions in environments where not everyone is fully-vaccinated?
    • I'm not quite sure how to use the microcovid calculator to gauge risk in "mixed" settings - does anyone know if they incorporate vaccination rates in your area when you select "I don't know" in response to "Their vaccine"?
      • It seems like they might, because for a given scenario, answering that question with "Yes" yielded 40 microCOVIDs, "No" yielded 400, and "I don't know" yielded 100, which is much closer to "Yes" than "No". But I haven't thought though the math.
  • How risky is it to do risky activities (say, kissing, sharing drinks) with people who are fully vaccinated but regularly doing those activities with unvaccinated people?

Rationale:

(#1 and 2 drive my decision to take the precautions I am still taking. #3 drives my decision to relax precautions otherwise.)

(1) Current vaccines are less effective against the Delta variant (confidence: medium-high)

• The mRNA vaccines are in the 80+% range and J&J's in the 60% effectiveness range against symptomatic COVID for the Delta variant (De-Lin 6/23/21)
• The WHO is urging fully vaccinated people to continue to wear masks given the Delta variant (CNBC 6/25/21), and the WSJ reported that about half of adults infected in an outbreak of the delta variant in Israel were fully vaccinated with Pfizer, prompting the government there to reimpose and indoor mask requirement and other measures (WSJ 6/25/21)
• However:
  • Public health experts cited by the NYT say the Delta variant is "unlikely to pose much risk to people who have been fully vaccinated."
    • “If you’re fully vaccinated, I would largely not worry about it,” said Dr. Ashish K. Jha, dean of the Brown University School of Public Health.
    • According to one recent study, the Pfizer-BioNTech vaccine was 88 percent effective at protecting against symptomatic disease caused by Delta, nearly matching its 93 percent effectiveness against the Alpha variant. But a single dose of the vaccine was just 33 percent effective against Delta, the study found.
    • “Fully immunized individuals should do well with this new phase of the epidemic,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. “However, the protection offered by a single dose appears low, and of course if you are not at all vaccinated, consider yourself at high risk.” (NYT 6/22/21)
    • That is despite the following, mentioned earlier in the same article:
      • "Delta, formerly known as B.1.617.2, is believed to be the most transmissible variant yet, spreading more easily than both the original strain of the virus and the Alpha variant first identified in Britain. Public health officials there have said that Delta could be 50 percent more contagious than Alpha, though precise estimates of its infectiousness vary.
      • Other evidence suggests that the variant may be able to partially evade the antibodies made by the body after a coronavirus infection or vaccination. And the variant may also render certain monoclonal antibody treatments less effective, the C.D.C. notes.
      • Delta may also cause more severe illness. A recent Scottish study, for instance, found that people infected by the Delta variant were roughly twice as likely to be hospitalized than were those infected with Alpha. But uncertainties remain, scientists said."
• Fully vaccinated people tend to have milder symptoms, avoiding hospitalization and death - it seems the call for masks is driven largely by the goal of preventing community transmission [to the unvaccinated, I assume?] (De-Lin 6/26/21)

(2) There may be long-term adverse effects from COVID even if it doesn't require hospitalization, but the risk is low (confidence: low). 

• This article claims the risk is low but understudied: https://www.huffpost.com/entry/will-people-who-get-covid-post-vaccination-have-long-term-symptoms_l_60afda9be4b0ead279660672 (5/30/21)
• The following paper Zvi linked in his last roundup did not look at vaccination (which, per the article above, may be protective against long COVID), nor did it give a good sense of the practical impact of the effects it mentions:
  • "Paper documents loss of grey matter in the brain after getting Covid-19, including for those who were not hospitalized – hospitalization did not seem to impact the magnitude of this effect. You do not want to get Covid-19. Given the timing this does not provide information on vaccinated people who then still got infected, nor does it differentiate between severity levels beyond whether someone was hospitalized. I do not have a good sense of what size impact one should expect from the effect observed here – it’s easy for this type of thing to be quite impactful, and also easy for it to sound scary while not having much impact at all." (Zvi 6/24/21)

(3) Prior to the Delta variant being a major concern, prevailing guidance was that it was fine for fully-vaccinated people to interact in close quarters indoors without masks. My understanding is that this hasn't changed for fully-vaccinated people since then. (confidence: medium)

• NYT 4/22/21: In a crowd, mask. And when you are with unvaxxed people 2 of 3 outdoors, distanced, and masked. Keep one in a pocket going out.
  • When to mask
    • If you [or the other person are?] not vaccinated, make sure your activity meets two out of the following three conditions: outdoors, distanced and masked
    • And masks are still advised for both the vaccinated and unvaccinated if you find yourself in an outdoor crowd, according to the new C.D.C. guidelines. Standing shoulder to shoulder with strangers during an outdoor concert or a protest could increase risk, particularly for the unvaccinated.Recently while hiking without a mask, Dr. Marr said she still made an effort to keep her distance from large groups when the trail got crowded.
    • “If I was passing by a solo hiker it didn’t concern me,” said Dr. Marr. “But if I passed by a group of 10 hikers in a row, I stepped further off the path. The risk is still low, but at some point there could be a large enough pack of people that the risk could become appreciable.”
• AAMC 3/2/21: ok to hang w/fully vaccinated folks w/o masking, not unvaxxed, probably not indoor restaurants
  • Can two people who are fully vaccinated be with each other without masking? “The answer is a firm and definitive yes,” Gandhi says.
  • “If you are around other people who have been vaccinated, you can take that mask off and enjoy being with them,” Ranney adds.
  • Can a vaccinated person be around an unvaccinated person without masking? No. “While I’m almost positive that vaccination is going to take away transmission, if you had a little viral RNA in your nose, we would never want a vaccinated person to pass that on to an unvaccinated person,” Gandhi says. “So, mask around the unvaccinated until they are vaccinated too.”
  • Can two vaccinated people enjoy dinner in an indoor restaurant? Maybe. “Because these are such powerful vaccines, you should be able to go out to eat, especially right now, when most of the restaurants have extra ventilation and spacing and the waiters are all wearing masks,” Gandhi says.
  • Ranney is a bit more cautious. “A couple of months from now, when most of us are vaccinated, going back to restaurants is going to be very safe,” she says. “But right now, given the high rates of COVID in the community and the fact that the vaccines are not 100% effective, that would not be my first choice.” Instead, she would recommend having your vaccinated friends over for dinner in your home.
  • Can you hug your grandkids? While the vaccines aren’t likely to be available to children until later in 2021, Ranney plans to reunite her parents and children as soon as her parents are fully vaccinated. “The risk to them of getting really sick from COVID is quite low. But the risk to them emotionally from continuing to be separated from my kids is higher. It’s a risk-benefit equation. We’re not going to completely eliminate COVID from the world, so two weeks after my parents get their second dose, we’re going to get together.”
  • Can you fly or go to the gym? “If vaccinated, you can go to an indoor gym, fly (maintaining your masking for others), and start opening up your life,” Gandhi says.
• Good examples of the sorts of precautions to take in a variety of specific situations:
  • NYT 2021/05/17 https://www.nytimes.com/2021/05/17/opinion/mask-cdc-guidelines-experts.html?action=click&module=RelatedLinks&pgtype=Article
• Vaccine's protectiveness
  • Very few breakthrough infections [though variants TBD...?] (NYT 4/22/21)
    • The U.S. Centers for Disease Control and Prevention recently reported just 5,800 cases of breakthrough infections among 75 million vaccinated people. And the C.D.C. has said vaccinated friends and family members can safely spend time together, indoors and outdoors, without masks.
    • [Though note - variants TBD]
  • Vaxxed unlikely to spread virus. Variants TBD (JHSPH 4/8/21)
    • Details
      • Can we say with any degree of certainty that vaccinated people are unlikely to spread COVID to unvaccinated individuals?
        • The emerging data confirms what many of us thought would be the case—that not only do the vaccines stop symptomatic COVID, but they also make it highly unlikely that someone can even be infected at all. I think the preponderance of the evidence supports the fact that vaccinated individuals are not able to spread the virus.
      • What is known about the variants of concern and their ability to infect fully vaccinated individuals?
        • When it comes to variants, it is likely the case that it depends on the variant and depends on the vaccine. The B.1.1.7 variant (first identified in the U.K.) is one that vaccines appear robust against. The more concerning B.1.351 variant (first identified in South Africa) appears to pose problems for the J&J vaccine but not where it counts in terms of presenting serious disease, hospitalization, and death. Data on the P.1 variant (first identified in Brazil) is forthcoming, but I suspect it will be similar to the B1.351 variant.
  • Variant impact
    • Even with variants, that guidance holds (Nat Geo 4/21/21)
      • “If you’re vaccinated, you can pretty much assume that you are protected against severe disease and very likely protected against enough infection to transmit, but because we have these variants emerging and the fact that we’re not even close to herd immunity, people should still be taking precautions,” Morrison says.Interacting with other vaccinated people without masks makes sense, but she also agrees with the CDC recommendation for vaccinated people to visit without masks or social distancing only with low-risk unvaccinated people in a single household. With so many infections still occurring daily, that limitation further reduces the likelihood of vaccinated people picking up and spreading infections from an unvaccinated home.“The real worry is for the unvaccinated people you come into contact with,” she adds. “Even if the potential for them to pass it on to you is low, it’s not zero.” Similarly, an infected vaccinated person has lower—but not a zero—likelihood of infecting others who aren’t vaccinated or have conditions or medications suppressing their immune systems.
    • Preliminary indication they protect against UK (B.1.1.7), impact severity with S Af (B.1.351) and Brazilian (P.1) (AAMC 3/2/21)
      • Myth #4: The variants are going to get us anyway, vaccines or not.For the last few months, concern has been growing that a number of SARS-CoV-2 variants — mutated versions of the virus that seem to be contributing to greater numbers of hospitalizations and deaths in some parts of the world — could render the vaccines impotent.The important thing to remember is that not all variants are the same, says Frieman. Emerging data from Pfizer, Moderna, and Johnson & Johnson, as well as the vaccine candidates from Novavax and AstraZeneca that are not yet approved by the Food and Drug Administration, suggest that all of these vaccines are highly protective against both the original virus and the so-called U.K. variant — also known as the B.1.1.7 variant — that is projected to become the dominant strain in the United States by the end of March.“The general consensus is that if you are vaccinated with any of the vaccines that we have now [including the vaccines from Novavax and AstraZeneca], you are protected against the 2020 strains and the U.K. variant,” Frieman notes.The so-called South African variant, technically known as B.1.351, and the Brazilian variant, known as P.1, are similar and do not seem to be as easily neutralized by the vaccines, Sette says. But that doesn’t mean the vaccines are completely useless. “We have been doing some calculations and it seems that most of the pieces that the T cells recognize are not changed in the variants,” he says. “What that means is that the T cell response [induced by the vaccine] may not prevent infection, but it can impact disease severity.”Gandhi agrees. “We are talking about the variants as if our T cell responses stimulated by the vaccine are not important. But they’re very important in preventing severe disease. And that matters because we never would have been in this mess with SARS-CoV-2 if it didn’t cause severe disease.”
• Official CDC guidelines (4/2/21)
  • https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html
• Sources
  • AAMC 3/2/21: https://www.aamc.org/news-insights/6-myths-about-covid-19-vaccines-debunked
  • JHSPH 4/8/21: https://www.jhsph.edu/covid-19/articles/new-data-on-covid-19-transmission-by-vaccinated-individuals.html
  • Nat Geo 4/21/21: https://www.nationalgeographic.com/science/article/yes-vaccines-block-most-transmission-of-covid-19
  • NYT 4/22/21: https://www.nytimes.com/2021/04/22/well/live/covid-masks-outdoors.html?campaign_id=9&emc=edit_nn_20210506&instance_id=30319&nl=the-morning&regi_id=61853201&segment_id=57358&te=1&user_id=f21d06cb83500399f474a90ef326937f
  • NYT 2021/05/17 https://www.nytimes.com/2021/05/17/opinion/mask-cdc-guidelines-experts.html?action=click&module=RelatedLinks&pgtype=Article