It appears that vaccination lowers the risk of Long Covid symptoms by a small margin—15%. This is in contrast to indications from earlier findings.
Nature Medicine published a study yesterday (May 25) detailing the results of analysis of persons who had been treated through Veterans Affairs. A cohort of those who had suffered breakthrough infections (BTI) after vaccination was compared with that of persons who had contracted SARS-CoV-2 without ever having received a vaccine. Separately, in a gauge of severity, those who had been hospitalized with SARS-CoV-2 were compared to those hospitalized with seasonal influenza.
In all, the study “buil[t] a cohort of 33,940 individuals with BTI and several controls of people without evidence of SARS-CoV-2 infection, including contemporary (n = 4,983,491), historical (n = 5,785,273) and vaccinated (n = 2,566,369) controls.” The data was drawn from January 2021 to November 2021, meaning that the data reflects the state of the pandemic before the Omicron variant came to dominate the landscape.
Findings
Compared to people with SARS-CoV-2 infection who were not previously vaccinated (n = 113,474), people with BTI exhibited lower risks of death (HR = 0.66, 95% CI: 0.58, 0.74) and incident post-acute sequelae (HR = 0.85, 95% CI: 0.82, 0.89). Altogether, the findings suggest that vaccination before infection confers only partial protection in the post-acute phase of the disease; hence, reliance on it as a sole mitigation strategy may not optimally reduce long-term health consequences of SARS-CoV-2 infection.
(HR = hazard ratio; CI = confidence interval) (emphasis added)
Thus, the study showed that prior vaccination reduced risk of death by one-third, while the risk for incurring any symptom or complication of Long Covid (that is, per the World Health Organization, post-acute sequelae “that last for at least two months and cannot be explained by alternate diagnoses”) decreased only by 15%.
The Washington Post reports:
Six months after their initial diagnosis of covid, people in the study who were vaccinated had only a slightly reduced risk of getting long covid — 15 percent overall. The greatest benefit appeared to be in reducing blood clotting and lung complications. But there was no difference between the vaccinated and unvaccinated when it came to longer-term risks of neurological issues, gastrointestinal symptoms, kidney failure and other conditions.
Context
That there were significant reductions in hypercoagulopathy and hematologic complications is a bright spot in the findings. The increased risk of blood clotting has been chronicled before—a 33-fold increase, in some populations.
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Still, that there was no statistically significant difference in these other areas (neurological, gastrointestinal, renal) is a deflating discovery. There had been hope that vaccination would confer not only protection against death (which the VA study confirms) but also against persistent symptomology. Previously, the UK Health Security Agency and research from Israel had indicated that vaccination could significantly guard against Long Covid symptoms, perhaps by as much as 50%. At best, taken with these new findings, the previous indications are now in doubt.
This study comes on the heels of other COVID-19 news this week, where scientists confirmed that “[d]amage to the body’s organs including the lungs and kidneys is common in people who were admitted to hospital with Covid, with one in eight found to have heart inflammation” (i.e., myocarditis). Though in that study “few participants had received a Covid jab,” in the context of Long Covid the results become newly relevant. If the VA results stand as robustly as its strength of numbers would suggest, then the persistent disease of these organ systems can be expected to be among those found among the post-acute sequelae population at just these rates.
Limitations
Keep in mind that the VA study, like all studies utilizing data from that particular sector, has limitations in terms of population. The Washington Post reminds us that “[w]hile the study population contained a wide range of ages and racial and ethnic backgrounds, it did skew older, Whiter and more male than the United States as a whole.” As the authors of the study state, only 8-10% of the people in their patient pool are female.
Takeaway
Still, the information should be placed in broader context. It appears that there is good reason to believe that vaccination is not enough to shield a person from the risk of Long Covid—at least, there is no full scientific consensus. As the authors caution, “The findings emphasize the need for continued optimization of strategies for primary prevention of BTI[.]” These mitigation factors would include what we already have implemented in the past, like social distancing and wearing high-filtration masks.
The study’s authors summarize:
Our analyses of BTI versus SARS-CoV-2 infection without prior vaccination show that, comparatively, the magnitude of the risks of death and post-acute sequelae was lower in people with BTI versus those with SARS-CoV-2 infection who had not been previously vaccinated for it. These results show that, although vaccination may partially reduce the risks of post-acute death and disease, to most optimally reduce this burden requires continued emphasis on primary prevention of breakthrough SARS-CoV-2 infection as a goal of public health policy.
Taken all together, these findings strongly suggest maintaining multiple strategies for mitigating one’s risk of SARS-CoV-2 exposure. Resist peer pressure to go maskless—take steps to secure your health. Mask, distance, and stay up on your vaccination and booster schedules.