Post-COVID-19 conditions: Lessons from Latin America

In Latin America, vaccination coverage for COVID-19 has been uneven. By April 2022, over 70% of the population had received the primary series (two doses), yet access and uptake varied considerably across countries. (1) Within this context, post-COVID-19 conditions, or PCC, remain an underexplored syndrome in the region. The scarcity of studies assessing vaccination as a preventive tool for long COVID highlights an important research gap.

PCC are estimated to affect 20% to 30% of unvaccinated individuals within three to six months of SARS-CoV-2 infection. (3) This reinforces the critical role of vaccination in reducing the long-term consequences of COVID-19.

Challenges within public health systems, combined with limited awareness among health care providers of the wide phenotypic spectrum of PCC, further complicate recognition and diagnosis.

Evidence suggests that SARS-CoV-2 immunization, particularly with multiple doses, reduces the risk of long COVID. A systematic review and meta-analysis by Watanabe et al. found that two vaccine doses lowered the risk of PCC compared with no vaccination (odds ratio = 0.64; 95% confidence interval, 0.45-0.92) and provided a significant advantage over a single dose (OR = 0.60; 95% CI, 0.43–0.83). (5)

Variations across Latin America

Latin American findings, however, are mixed. Some studies have reported no protective effect from one or two doses (2, 4) while others have observed a reduction in risk with three or more doses. (3, 6) These results contrast with large European population-based studies, where vaccination was strongly associated with a reduced probability of long COVID. (5, 16) 

The protective effect of additional doses aligns with proposed mechanisms, including reduced viral persistence, improved vascular and endothelial function, stabilization of vagal signaling and modulation of immune dysregulation. (6, 7) Yet neutral results in some Latin American studies suggest that individual and regional factors such as sex, age (5, 8) and comorbidity burden (diabetes, hypertension, dyslipidemia, obesity) — may influence vaccine efficacy.

In Mexican and Brazilian cohorts, PCC patients were typically older, with more comorbidities, and more often unvaccinated individuals who had required supplemental oxygen during acute infection. (8, 9) While Marra and Núñez reported higher PCC prevalence in men (4, 8), Angarita’s Hispanic cohort found greater odds among women and unvaccinated patients with hypertension or diabetes (10), consistent with other Mexican reports. (10) Importantly, this multicenter cohort including Ecuadorian participants (15) described a higher prevalence of sequelae in unvaccinated men or those with only one dose. These patients were more likely to experience respiratory and metabolic complications and to require oxygen support during acute illness.

Across Latin American studies (3), hypertension and diabetes were the most common comorbidities, even among health care workers. Notably, one of these studies incorporated genomic sequencing to identify circulating variants, showing that vaccinated individuals were less likely to develop PCC than those infected before vaccination. Reinfection emerged as a strong risk factor, whereas continued immunization appeared protective. (11)

Consistent definitions lacking

The timing of vaccination before or after infection (12), the variant in circulation (Delta vs. Omicron) and vaccine type (5) may all influence outcomes. However, the lack of consistent definitions of PCC complicates the evaluation of severity and duration. Large studies suggest vaccination decreases severe cardiovascular and thromboembolic sequelae of long COVID. Similarly, individuals receiving multiple boosters demonstrated a markedly reduced risk of PCC (12), and some evidence indicates that vaccination with two or more doses may accelerate recovery, reducing symptom persistence. (3)

One Mexican hospitalized cohort offered a rare phenotypic characterization of PCC, describing six phenotypes (respiratory, mucocutaneous, neurological, functional, gastrointestinal and mood/sleep/cognitive disorders) across 23 symptoms, with a median follow-up of 405 days. (9) They found no clear reduction in specific phenotypes among vaccinated patients, raising the possibility that distinct phenotypes may respond differently to immunization, as suggested in other cohorts. (5)

Taken together, the evidence from Latin America suggests that COVID-19 vaccination can reduce both the incidence and duration of PCC, but population characteristics, timing and vaccination regimens likely shape its effectiveness. The growing regional data highlight PCC as a major public health challenge. There is an urgent need for region-specific research to clarify how vaccination can best prevent these long-term outcomes. (15, 16)

Broader vaccination concerns

Finally, actions by decision-makers such as U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr., known for his antivaccine views and comments, are of great concern. His changes to the U.S. Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices are already affecting vaccine access in the U.S. and creating confusion among the public.

Between 2024 and 2025, the percentage of vaccinated children fell to 92.5% for the measles, mumps and rubella vaccine and to 92.1% for diphtheria, tetanus and pertussis, according to CDC data. Although these are still very high immunization levels, they are insufficient to guarantee herd immunity, which requires 95% coverage. (17)

All of these developments have a global impact, primarily in unprotected regions such as Latin America and Africa, where there is a struggle to obtain vaccines important for global health.

References

1. CDC. Long COVID or Post-COVID Conditions. 2023.
2. Signore IA, Donoso G, Bocchieri P, Tobar-Calfucoy EA, et al. The Chilean COVID-19 Genomics Network Biorepository: A Resource for Multi-Omics Studies of COVID-19 and Long COVID in a Latin American Population. Genes. 2024;15:1352.
3. Neves Amorim CE, Silveira Cazetta G, Pontello Cristelli M., et al. Long COVID Among Kidney Transplant Recipients Appears to Be Attenuated During the Omicron Predominance. Transplantation. 2023;108: 963-969.
4. Marra AR, Sampaio VS, Ozahata MC, et al. Risk Factors for Long Coronavirus Disease 2019 (Long COVID) Among Healthcare Personnel in Brazil, 2020-2022. Infect Control Hosp Epidemiol. 2023;44:1972-1978.
5. Watanabe A, Iwagami M, Yasuhara J, et al. Protective effect of COVID-19 vaccination against long COVID syndrome: A systematic review and meta-analysis. Vaccine. 2023;41:1783-1790.
6. Peluso MJ, Swank ZN, Goldberg SA, et al. Plasma-based antigen persistence in the post-acute phase of COVID-19. Lancet Infect Dis. 2024;24:e345-e347.
7. WHO. Statement on the Antigen Composition of COVD-19 Vaccines. April 26, 2024. Accessed Nov. 20, 2024.
8. Núñez I, Gillard J, Fragoso-Saavedra S, et al. Longitudinal clinical phenotyping of post COVID condition in Mexican adults recovering from severe COVID-19: A prospective cohort study. Front Med. 2023;10:1236702.
9. Del Carpio-Orantes L, Trelles-Hernández D, García-Méndez S, et al. Clinical-epidemiological characterization of patients with long COVID in Mexico. Gac Med Mex. 2024;160:144-151.
10. Angarita-Fonseca A, Torres-Castro R, Benavides-Cordoba V., et al. Exploring long COVID condition in Latin America: Its impact on patients’ activities and associated healthcare use. Front Med. 2023;10:1168628.
11. Peters MDJ, Godfrey C, McInerney P, Khalil H, et al. Best practice guidance and reporting items for the development of scoping review protocols. JBI Evid Synth. 2022, 20, 953-968.
12. Gao P, Liu J, Liu M. Effect of COVID-19 Vaccines on Reducing the Risk of Long COVID in the Real World: A Systematic Review and Meta-Analysis. Int J Environ Res Public Health. 2022;19-12422.
13. Fuller T, Flores Mamani R, Ferreira Pinto Santos H, et al. Sex, vaccination status, and comorbidities influence long COVID persistence. J Infect Public Health. 2024;17:102562.
14. Azambuja P, Bastos LSL, Batista-da-Silva AA, et al. Prevalence, risk factors, and impact of long COVID in a socially vulnerable community in Brazil: A prospective cohort study. Lancet Reg Health. 2024;37:100839.
15. Arango-Ibanez JP, Córdoba-Melo BD, Gutiérrez Posso JM, et al. Long COVID Clusters of Symptoms Persist beyond Two Years after Infection: Insights from the CARDIO COVID 20-21 Registry. Viruses. 2024;16(7):1028.
16. Zambrano-Sánchez G, Rivadeneira J, Manterola C, et al. Immunization as Protection Against Long COVID in the Americas: A Scoping Review. Vaccines. 2025;13(8):822.
17. Vidal Liy M. El hombre que no amaba las vacunas: Robert F. Kennedy, secretario de Salud de EE UU. El Pais. Sept. 6, 2025.