COVID-19 Vaccines Probably Prevent PASC (long COVID-19)
The gist: While we do need well-designed prospective studies that look explicitly at whether or not vaccines prevent long COVID, and those studies are underway, we know that you need to get infected with SARS-CoV-2 to develop long COVID. We have quite a bit of data to show that vaccines do in fact prevent that, both by preventing direct infection of the vaccinated individual and by blocking subsequent transmission of the virus. For that reason, it’s likely that COVID-19 vaccines do in fact prevent long COVID.
COVID-19 has surprised us in many ways, but among the most frustrating is PASC (post-acute sequelae of SARS-CoV-2 infection). The condition is reviewed in detail here, and it’s worth noting that neuropsychiatric sequelae are substantial. Patients can look forward to any number of symptoms including shortness of breath, decreased exercise tolerance, blood clots, palpitations, chest pain, anosmia, parosmia, ageusia, brain fog, anxiety, depression, sleep disturbances, PTSD, hair loss, and more. It’s hard to predict who gets it, but some identified risk factors include female sex, being older, and having a higher BMI. Notably, it seems to occur with any severity of COVID-19, and has been reported even among asymptomatic patients or those with mild disease. Thus there’s a really critical question: do the vaccines prevent PASC? Well, HEAL-COVID is a study that aims to find out- but truthfully, I think there are significant hints already that COVID-19 vaccines prevent PASC. Prospective studies to answer the question explicitly like HEAL-COVID should absolutely still be done, but there’s one thing we know about PASC for sure: you have to be infected by SARS-CoV-2 to get it. We have a great deal of data showing quite clearly that the vaccines can prevent that. Here’s a non-comprehensive sampling:
There’s this summary of the indirect effects observed with COVID-19 vaccines which discusses some of the data showing they can prevent infection.
This study found that 14 days after the second dose of an mRNA vaccine, the risk of a positive PCR was 90% lower than for an unvaccinated individual.
The prevention of infection is known as sterilizing immunity and it is a process mediated by antibodies. In Pfizer’s recent trial of those aged 12-15 years, the geometric mean titers (GMTs) of antibodies were even higher than in the 16-25 year-old group. These titers were taken from plasma though, and it is mucosal antibodies within the respiratory tract, especially the upper respiratory tract, which would mediate prevention of SARS-CoV-2 infection- but given the data that infection risk is reduced in adults, and that at least some of the antibodies from plasma (though notably NOT IgA) are transported to the mucosa, it is reasonable to presume that the effects of this parenteral vaccine extend to children at least as well.
The SIREN study of UK healthcare workers confirmed that the Pfizer vaccine is able to reduce the risk of asymptomatic infection by 85% 7+ days after the second dose.
In a nationwide study in Israel, the Pfizer vaccine was able to reduce asymptomatic infection by 90% 7 days after dose 2.
A study of Mayo Clinic patients found that 10 days after 1 dose of mRNA vaccination, the risk of a positive PCR was reduced by about 80%.
Johnson and Johnson/Janssen’s pre-licensure Phase 3 trial measured an efficacy of 65% against asymptomatic infection.
You also can’t get COVID-19 if it’s not circulating in the community, and that gets more feasible with fewer people susceptible to infection. Each of the aforementioned studies also show that vaccines contribute directly to herd immunity and reduce the spread of virus because you can’t spread a virus you haven’t been infected by. Studies have also been done that explicitly demonstrate vaccines reduce transmission to unvaccinated people:
This study showed that for every 20% of the population that is vaccinated, the risk of an unvaccinated person having a positive PCR is halved.
This preprint showed that vaccination of healthcare workers reduced their household’s risk of developing COVID-19 and needing hospitalization by about 30%, and 54% if they had 2 doses.
Another study in England found that the likelihood of household transmission is 40-50% lower for households in which the index cases are vaccinated 21 days or more prior to testing positive (compared to no vaccination), with similar effects for both ChAdOx1 nCoV-19 and BNT162b2 vaccines; however most individuals in the study received a single dose of vaccine.
It’s worth noting that most of these studies are examining mRNA vaccines, so we need more data about other technologies, but I do think it’s reasonable to assume the findings generalize, at least partially, until evidence emerges to suggest otherwise.
