Test, Triage, And Trust the Vaccine
My patient called me in a panic. Her vaccinated husband developed a cough and runny nose hours before her extended family was to arrive from out of town. With the highly contagious Delta variant, we know that breakthrough infections (i.e. infections in fully vaccinated people) are no longer rare.
Well aware that most people with a breakthrough COVID infection have mild symptoms, my patient nonetheless went into fight-or-flight mode — I’d do the same! — as she mulled the various scenarios about to unfold as higher-risk grandparents, a brother recovering from a heart procedure, and her unvaccinated niece flew in for a long-awaited visit.
By phone I counseled her to consider a rapid test (aka a “contagiousness” test) and to consult with her husband’s doctor. Within 15 minutes they had an answer: negative.
What are the current COVID testing options?
Rapid antigen testing:
In people tested within 7 days of symptoms onset, the rapid antigen test (like Abbott’s BinaxNow) offers a sensitivity of 84.6% in children and 96.5% in adults. This means that, especially in adults, there are very few false negatives, making it very useful in picking up a positive COVID case during the infectious period. The test also has a specificity of 100% (almost no false positives) — meaning that a positive test is almost certainly a true positive.
The cases it misses (lower sensitivity) are on either side of the infectious period: in the two days right after exposure while the virus is replicating, and on the tail end during recovery. In other words, the high level of sensitivity means that in symptomatic adults the rapid test does a very good job of identifying those without COVID-19 as being negative. It’s a little less sensitive in identifying cases in kids which is yet another reason to have a trusted pediatrician.
The bottom line: The rapid test, while not inexpensive (Abbott BinaxNow is $24 for a two-pack) can be useful in quickly identifying whether or not your sick (vaccinated or unvaccinated) household member has infectious levels of coronavirus in their nose. This can help you decide if you need to cancel a dinner gathering or avoid sending your exposed child to daycare, camp, or school.
For non-sick people, the rapid antigen test is less sensitive overall — which is why I don’t use it for one-off, random testing. That said, when used FREQUENTLY in non-sick people, rapid antigen tests can serve as another layer of protection against silent household transmission as my friend Michael Mina at The Harvard School of Public Health has been advocating since 2020. I highly recommend watching this brief video explaining the utility of rapid tests in helping prevent community spread and keeping kids in school.
PCR testing
In contrast to the rapid antigen tests, PCR tests have higher sensitivity (i.e. they will find people very early in infection (before they are infectious and before the rapid test catches them), and also later in infection, after they are no longer infectious. The PCR test can take a few days longer to get results and also can remain positive for up to 12 weeks after infection.
I use PCR testing in non-sick vaccinated people who’ve been exposed to COVID-19. I also recommend it for people whose symptoms and clinical history suggest a diagnosis of COVID-19 but who have a negative rapid antigen test — or to confirm a positive antigen test as needed. (Pictured here is me in my garage this morning!)
Particularly as fall and winter approaches, the concomitant use of PCR tests for COVID-19, flu, RSV (already circulating widely) will be critical. There’s no at-home testing for the latter two, and distinguishing between these viruses — which is not hard with testing! — is important for management decisions re: isolation, quarantine, and household contacts. Moreover, testing for common respiratory pathogens among kids will be crucial to help limit unnecessary quarantines and missed school and daycare — and work days for their caregivers.
What does the CDC say about testing, isolating, and quarantining fully vaccinated people?
If sick:
The CDC recommends that symptomatic, vaccinated people get tested for COVID-19. They should stay home for 10 days from the positive test or onset of symptoms (same recommendations as for the unvaccinated). This, again, is where a rapid antigen test is helpful.
If exposed to COVID-19:
If symptomatic, see above.
If not symptomatic, fully vaccinated people do not need to quarantine. They should self-monitor for symptoms for 14 days and get tested 3-5 days after exposure (ideally with PCR).
Dealing with colds and breakthrough infections
I’m seeing LOTS of non-COVID colds. I’m also seeing some cases of COVID-19 in fully vaccinated patients. This mirrors what the data reveals — that the highly transmissible Delta variant is driving up infections, mostly in unvaccinated people but also in some vaccinated folks as well.
As expected, most of my patients with breakthrough infections are experiencing cold or mild flu symptoms that can be managed with rest, hydration, ibuprofen or acetaminophen for aches or fever, and decongestants. But checking in with your doctor and reporting any escalating symptoms (like shortness of breath) is critical. And remember that monoclonal antibodies are available for those age 12 or older who have risk factors for serious disease.
To isolate a sick person at home, try to provide solo sleeping and bathroom areas if possible, don’t eat together, increase ventilation by opening windows, wear a mask indoors, and wash your hands frequently. It is possible to keep COVID-19 from going through the household: secondary attack rates range from very low if the first patient is a child with no symptoms to approximately 20%-40% if the patient is a sick adult.
Is it true that vaccinated people can infect other people?
If symptomatic: Yes. Symptomatic people can sicken other people — even if they’ve been vaccinated. This is not a surprise, nor is it unique to COVID-19. This is why we stay home and avoid other people when we’re sick with any respiratory infection.
If asymptomatic: Yes, but it’s less likely that a vaccinated person will silently spread the virus compared to an asymptomatic unvaccinated person. Before Delta came along, asymptomatic infection (and forward transmission of the virus) was rare after vaccination. Not surprisingly with Delta, transmission by vaccinated people is still unlikely but seems to be happening more often than with the ancestral strain of the virus.
The Provincetown story ignited scary headlines suggesting that vaccinated people are equally likely to spread coronavirus as unvaccinated people without data to support this claim. This is not accurate. Just last week, real-world data out of the Netherlands backed up earlier data from Singapore — and showed that vaccinated people can indeed carry high levels of detectable viral particles in their nose, but the viral particles are less likely to be viable (able to infect others), and the period of significant viral shedding is shorter because vaccinated people clear the virus faster (thanks to vaccine-induced IgA antibodies that line the inside of our noses).
Also please remember: You cannot transmit the virus to other people if you aren’t infected in the first place. Since vaccinated people are less likely to get infected, they’re less likely to transmit the virus to others.
OK, so what about booster shots?
The hot question right now — particularly with today’s full FDA approval of Pfizer’s vaccine — is this: With Delta causing more vaccinated people to have symptomatic and asymptomatic infections, don’t we ALL need booster shots NOW?
The short answer is no. (See this Tweet from the GODFATHER of virology, Dr. Vincent Racaniello).
The vaccines continue to be extraordinarily effective against death and hospitalization — even against Delta. Real-world data out of Denmark last week showed 94% effectiveness of two doses of Pfizer and 97% effectiveness of two doses of Moderna against severe illness. (Please note that these percentages reflect relative risk reduction comparing a vaccinated group against an unvaccinated group and does NOT mean, for example, that a Pfizer recipient has a 6% chance of being hospitalized from COVID-19.)
What we are seeing is reduced overall immune protection against infection with the Delta variant. In Denmark's data, the effectiveness against symptomatic infection for Pfizer dropped to 79%, Moderna to 88%. While this might sound terrifying at first glance, there’s a lot more to it. First, the vaccines were never designed to prevent every single possible infection. That was never on the menu. What reduced effectiveness against overall infection with preserved excellent protection against death and severe disease means is this: infections are more common — and therefore the populations who are at highest risk (should they be unlucky enough to get infected) should get a third dose. These include people who are highly immunocompromised or who live in nursing homes, for example.
What about people who received the J&J shot? A robust South African trial this month showed that this single shot was 71% effective against hospitalization and 96% against death from Delta. To me, this is a very good reason for J&J recipients to have a single dose of an mRNA shot (Pfizer or Moderna), and I’d be surprised if the FDA and CDC don’t authorize that soon.
In the meantime, recall that the best way to prevent severe disease — and the best way to contain the virus on a population level — is to get the primary vaccine series. The best way to protect unvaccinated kids is to surround them with vaccinated people. (See here for a more nuanced discussion about kids on Al-Jazeera with my co-panelists, both hospital-based pediatric specialists.)
A breakthrough infection that causes a cold or three days in bed is not — in and of itself — proof of vaccine failure. Nor does the normal waning of antibody levels after an infection or vaccination necessarily equate to waning immunity. But wouldn’t a third dose top up antibody levels and likely be safe? Probably yes! And couldn’t a booster shot help prevent mild or moderate symptoms in everyone? Maybe!
But the real question is this: is a third dose necessary? (A book I'd love to write some day would be entitled, Just Because We Can, Doesn't Mean We Should.)
Let’s remember that after we are vaccinated or infected with COVID, our immune systems are poised to make fresh batches of antibodies should we get (re)exposed to coronavirus — and our T cells do much of the heavy lifting to prevent us from severe disease. I will say this again: the normal waning of antibody levels after vaccination or infection is not synonymous with dropping vaccine effectiveness. Vaccine effectiveness does NOT drop off a cliff at eight months.
(Here is a great “explainer” about our immune system and boosters by infectious disease and ICU doctor Amesh Adalja, MD.)
Big picture: a dip in vaccine effectiveness against infections that don’t land people in the hospital isn’t necessarily a reason for policy-makers to boost the whole country. But drops in vaccine effectiveness against the primary endpoints of death and hospitalization would.
It would be impossible for the CDC to understand the complexities of our individual medical conditions, living situations, workplace exposures, community transmission and immune status — all of which inform our chances of getting sick — which is why I hope the CDC dispenses nuanced advice to make sure we protect our most vulnerable populations first.
What about mixing and matching vaccines? Studies out of the UK suggest the mix-and-match approach actually triggers a stronger immune response than two doses of the same vaccine. In Germany too, patients have been receiving the mixing vaccine types without any major safety issues. In short, I have no problem with a patient who had the initial Pfizer series get a booster with Moderna — or vice versa.
A final word about the vaccines and boosters. It’s critical to manage our expectations about what vaccines can and cannot do. As you know, this virus isn’t going away. Population immunity (through vaccination and natural infection) will help contain it, limiting ongoing death and destruction. But eliminating COVID altogether simply isn’t possible. The virus will become endemic, just like the four other common coronaviruses known to cause the common cold.
This is not to say we shouldn’t do everything we possibly can — using scientific evidence as our guide — to stomp out COVID-19. It’s also not to say that death is the only outcome we care about in medicine. As someone whose career is founded on preventing and managing chronic illness, I’ll sing this tune from the hilltops: Preventing death is important, but quality of life matters, too! It's that we cannot expect a COVID-free future. However with highly effective vaccines and broad population immunity, we will continue to turn coronavirus into its wimpier cousin and begin to reclaim some semblance of normalcy, however that may look.
For now, I will continue to guide my patients one at a time, recommend boosters to people who need them, and help you decode more data as it emerges. The pandemic keeps all of us on our toes. As always, I will keep you posted! (Here’s me today on WJLA Channel 7 attempting to do just that.)
I will see you next week. Until then, be well.