As Delta variant spreads, the pandemic parameters have changed: are COVID-19 vaccine boosters needed?

With the rapid rise of COVID-19 cases due to the Delta variant in unvaccinated individuals much of what we thought we knew about the pandemic has changed.

Bob Wachter, UCSF’s Chair of Medicine, summarized these rapid changes recently in an excellent tweetorial:

Wachter references another tweetorial (written by epidemiologist @EpiEllie) which estimates the Delta variant is 2.5 times more infectious than the original virus:

With a virus that’s 2.5 times more infectious, levels of immunity that would have tamped down the spread of the old virus are no longer adequate to do so with Delta


One topic I’ve been pondering since I’m “old” and was vaccinated 8 months ago is a booster shot.

Wachter identifies 4 groups that will need boosters:

Speaking of being unprotected, the next battleground will be over boosters. So much of Covid has pitted individual rights/choices vs. community need. There now seems little doubt that 4 groups will need boosters to deal w/ waning or inadequate immunity from vaccines. a) Immunocompromised; b) Elders (?age); c) vax w/ J&J; & d) vaxxed >6 mths ago. My read of evidence: it would be reasonable to offer boosters to all 4 groups today – if the only issue was risks vs benefits to them as individuals

After discussing vaccine availability and issues related to tracking vaccination he concludes that those groups should be getting boosters ASAP

solution: approve boosters for those 4 groups ASAP as long as vax surplus holds (evidence seems persuasive that benefits outweigh risks), as several European countries have done.  My guess is that FDA/CDC are also hesitating on boosters because they fear that green-lighting them will send a message to some vax-hesitant folks that vaccines don’t work. I get that, but these kind of Covid mind games (other: call breakthrough infections “rare” so as not to discourage vax) don’t work & serve to undermine credibility.

Those of you who are unvaccinated, for your own health and the health of those around you please get vaccinated ASAP!

It’s obvious what an unvaccinated person should do: get vaccinated ASAP, and stay super-safe until fully vaxxed (remember, shot #1 doesn’t protect against Delta the way it used to). Particularly in a high case prevalence region, your chance of catching the virus has. never been higher, and – while treatments have improved – there’s still a decent chance of a stormy course, including Long Covid, hospitalization, and (depending on your risk factors) death. I’d be afraid. Yes, I’d be very afraid

Finally, Wachter details how the changes have changed his behaviour.

as a 63-year-old guy vaxxed w/ Pfizer in Dec-Jan, no booster yet, & living in still- fairly-low prevalence SF, what am I doing? I haven’t cancelled flights, though I will if trip’s elective. When I fly, I’m wearing N95 for the whole flight. In indoor spaces (stores, work)

I’m double masking (cloth/surgical). No more indoor dining, & sadly no more poker w/ vaxxed pals. I’ll peel off protections as cases fall, particularly after my booster.

You’ll make your own choices, but don’t underestimate Delta. As the CDC said, it’s a new war. 

Provaccinely Yours,



17 thoughts on “As Delta variant spreads, the pandemic parameters have changed: are COVID-19 vaccine boosters needed?”

  1. So the mRNA vaccines (Pfizer) are not very durable and ‘protection’ wanes at 180 days. How does a booster fix this? I am not going for anymore shots – I will not be duped into a semi-annual appointment with my pharmacist. Under 65y, zero comorbidities, jog 12 miles per week – CDC tells me 99.5% recovery from covid if I get covid – I’ll bank on those odds

    • Hopefully we will get data on the safety and effectiveness of boosters very soon. The Moderna CEO indicated yesterday they would be crafting them to focus on the delta variant. I would say the delta variant changes your calculus.
      Dr P

  2. Is it the case that the breakthrough infections – especially those that turn into severe Covid – are happening largely or exclusively in people whose immune systems are not responding to the vaccine (that is, not producing neutralizing antibodies and/or T cells)? If that is the case, do you think the brain trust will likely be able to fashion a test (perhaps taken a month after vaccination) to determine whether a vaccinated person’s immune response has kicked in – so that we would know if we are susceptible to a breakthrough or severe infection?

    • Rick,
      This is a question I have pondered extensively. I tested myself for antibodies several weeks after my second Pfizer injection and the test came back negative. This was done through Quest and likely was the wrong antibody test (nucleocapsid). Subsequently, about a month ago I underwent the new Labcorp semiquantitative spike antibody test and it came back positive (80) which was somewhat reassuring. After doing more reading, however, I realized that “neutralizing” antibody levels would be more germane and these are not really available outside research settings as far as I can tell. I talked to the transplant surgeon who found his T-cell response insufficient but his testing was done by colleagues at his academic center so not widely available.
      I’ll post something if I see a solution in this area.
      dr P

  3. Sign me up for the booster! As a volunteer first-responder I’m slipping back into the “what would I do” mode. Act? Delay? Walk away? I hate it.
    I had my 2 biggest breaks from pandemic protocol last weekend. Two life memorials, one with a Search and Rescue Captain who died. Memorial in a LDS church, likely <40% vaccination rate. Second was another large group, though likely >than 70% vaccination rate. I live in a “high” danger area. Rural, tourist. Hopefully I dodged the bullets.

    I have 8 simple rapid antigen tests coming from Amazon. Biocan $12 per test. Still more expensive then they should be. Fortunately I can afford them. I am deeply confounded why simple rapid antigen tests are not being deployed (paid for by government) in massive numbers. I discovered Dr. Michael Mina at the beginning of the pandemic. His (not really his, but the impressive group of people that make up the core of the expertise) website lays out compelling science based reasoning as to why they should be a critical tool in the tool box. Not a migic bullet, but a tool among many. I’ve lobbied my local, state and national elected officials. I’ve asked in covid forums put on by our local hospitals. Radio silence, deer in headlights from the politicians. The smart capable Doctors on the covid forums rolled out the talking points that Dr. Minas
    ( MD, PhD, Assistant Professor of Epidemiology, Harvard T. H. Chan School of Public Health) has thoroughly countered.

    With Delta (and now Lambda???) crushing our progress, what are we waiting for? Deploy simple rapid antigen tests now!! Gah….ugh.

      • Dr. P – First step FDA needs to remove the “medical device” categorization of simple rapid antigen tests, at least on an emergency basis. Or Biden just need to make it happen through executive order. This way prescriptions wont be required, allowing a streamlined approach for more companies to participate in the manufacturing. I didn’t need a prescription for my rapid antigen tests, but I believe it is because this was an FDA approved test. Biden already earmarked 230 million for rapid antigen tests in Feb, awarding one company the deal to produce them ($30 each variety). 19 million a month (8.5 million I believe goes to the Department of Defense). These are still the more expensive type tests. Dr. Minas claims $5 per test to user is totally possible and still give the approved companies plenty of margin, especially when produced at such a massive scale.
        Once the above is addressed, It’s a logistics challenge first and foremost. From my amateur’s post, I would gather the brightest minds at UPS, FedEx, DHL, United States Post Office, the Military etc. and ask them to lead the way. 2 tests a week in each Americans P.O. Box or mail box comes to mind. Included with empowering information on why we are being asked to test, and what to do if you come up positive. School distribution. Private business distribution. Sporting events. You name it. Make simple rapid antigen tests ubiquitous until we top the ridge on this mess.
        Next is messaging, in hopes people will use them. I fall firmly in the camp that the country and its people need straight talk. No more mind games (as was referenced in your post), no more tricks to attempt to outsmart the adults we all rely on to wake up and take this emergency as just that, an emergency. It may very be true that there are a whole barrel of not too smart fish out there, but most and likely all of those fish don’t like being treated like children (regardless if they are acting like them), talked down to, or belittled.
        Clearly vaccination is our way out of this, and until that becomes more embraced then we need to double down on education and testing. From what I have gathered we have missed the bus on contract tracing as a tool to stop this pandemic. No suggestion to abandon it, but testing is how we put water on this raging fire. PCR tests clearly have a critical role to play but they are too expensive for mass deployment, and require a trip to a hospital, clinic or pharmacy.
        Empower the American people to do the right thing, and give them a simple, private tool to do it, and I believe we will be surprised in the best way by the results.
        Dr. Mina and Co. address all of this and more on their website
        I’m very interested what your take is.

        Simple Rapid Testingly Yours (I couldn’t help myself)

        Radical Earthling

  4. What is your take on Covid survivors, the ~99.9% of us. Now we can’t go to NYC events or restaurants, Will have difficulty travelling overseas. – Why is the “political-medical” complex lumping us in with the the “unvaxed”. We are less of a threat than the vaxxed,

    • Do you have a source for your assertion that COVID survivors are “less of a threat than the vaxxed”? Thanks.

  5. Where can I go to see the “hard data” on how many of hese new cases result in hospitalizations and death? And how many have comorbidities, their age, etc.
    That specific data was readily available before.

  6. As a senior (age 68) in SW FL, I was vax’d in Dec ’20 – Jan ’21 with Moderna. So now, 7 months later in August ’21, I’m reportedly emerging from at least the highest level of protection that provided. I continue to mask indoors in public spaces.

    I’ve got an S-ICD (defibrillator), and as luck would have it I’ve just entered a 6 month window in which I’ll need to have a generator replacement (and possibly a new lead) as the battery is approacing it’s EOL. My area in FL (Naples) has relatively high vaccination rates and lower case rates (much lower than the Jacksonville area now being hit hard by Delta), so I’m meeting with my EP later this month to set up the outpatient procedure at a local hospital, probably in early September (before we get our waves of “snowbirds” from out of state and hopefully before any possible limitations on “elective” surgeries kick in if the Delta surge continues).

    So my question is… is that a better play than holding on the generator replacement a bit (running out the battery clock) pending a possible “booster” shot in the next few months? Would it be better to try (hypothetically, of course) and finagle a 3rd shot of the existing Moderna vax as a DIY “booster” until the promised “real” booster (tuned to the Delta variant) arrives? Or just stick with my original plan to get the surgery ASAP while my vax is still mostly effective?

    Dischargingly yours,


  7. Anthony,
    “One topic I’ve been pondering since I’m “old” and was vaccinated 8 months ago is a booster shot.”

    I’ve about the same as your condition (age: 76, 2nd Moderna 6 months ago). Great thread and I’m all in on getting the booster ASAP. Individually we may not be able to solve the worlds Covid problems but, whatever path we choose, it’s better when your not on a ventilator.


  8. Should we be more worried about getting ourselves boosters or about seeing to it that the rest of the unvaccinated world is provided with vaccines enough to diminish further likelihood of developing a truly horrific variant? The 3rd world petri dish.
    Or is that just too big a job? See to ourselves first?


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