The risk of developing long COVID appears to have declined as the COVID-19 pandemic progressed.

The research, which tracked nearly 500,000 individuals infected with COVID-19, revealed a notable decrease in long COVID rates corresponding with changes in the dominant virus strains and vaccination status.

The study observed that as the virus evolved from the original strain to the delta variant and subsequently to the omicron variant, the incidence of long COVID decreased. 

Specifically, there were 5.23 fewer instances of long COVID per 100 people during the omicron era compared to the pre-delta and delta periods combined. 

Vaccination played a crucial role, accounting for 72 per cent of this reduction.

“While the risks decreased during the pandemic, the risk of long COVID remained substantial even among vaccinated people infected during the omicron era,” the study's authors noted. 

Despite advancements in vaccinations and virus evolution, long COVID continues to be a significant health concern.

The research utilised health records from the Department of Veterans Affairs, focusing on a study population of 441,583 veterans with COVID-19 infection between March 2020 and January 2022, alongside 4,748,504 non-infected contemporaneous controls. 

It estimated the cumulative incidence of post-acute sequelae of SARS-CoV-2 infection (PASC) at one year after infection.

Among unvaccinated individuals, the cumulative incidence of long COVID was 10.42 events per 100 persons in the pre-delta era, 9.51 events during the delta era, and 7.76 events in the omicron era. 

For vaccinated individuals, the incidence was lower: 5.34 events during the delta era and 3.50 events during the omicron era.

The findings underline the importance of vaccination in mitigating long COVID risks and suggest that ongoing efforts to vaccinate the population remain vital. 

As the virus continues to evolve, understanding the interplay between virus strains and vaccination can help guide public health strategies to reduce the burden of long COVID.

The full study is accessible here.