Covid-19: Breakthrough infections raise risk of long Covid, death

The risks of long Covid and death are higher for unvaccinated people six months after catching Covid-19 than those who got jabbed, finds a new US study. Image / CDC

A major new US study has found breakthrough infections can come with a higher danger of long Covid and deaths months later - but unvaccinated people still remain most at risk from the virus.

In a paper just published in the journal Nature Medicine, researchers from the Veterans Affairs Saint Louis Health Care System analysed data from 13 million veterans.

The study, led by renowned epidemiologist and long Covid researcher Dr Ziyad Al-Aly, compared nearly 40,000 people who'd received a full round of vaccinations against control groups totalling about 13.3 million people.

Compared to not getting infected in the first place, vaccinated people who got a breakthrough infection (BTI) had a 1.75 times higher risk of death six months after getting sick - and a 1.5 times higher risk of symptoms linked to long Covid.

Furthermore, these risks after a breakthrough Covid infection were higher than in people with seasonal flu.

Vaccinated people hospitalised with BTI had a higher estimated risk of death (43.58 more deaths per 1000) and of developing symptoms of long Covid (87.59 additional people per 1000 who experienced at least one symptom) in the first 30 days after diagnosis than that of people hospitalised with seasonal influenza.

But there was a higher risk, still, for people who'd never received a jab.

During the first 30 days after diagnosis of Covid-19 as a result of a BTI, for vaccinated people, there were 10.99 fewer deaths per 1000 people - and 43.38 fewer people per 1000 who experienced at least one symptom – compared with unvaccinated people.

Those findings backed a range of studies that showed a person was significantly less likely to be severely sick, hospitalised or die from Omicron if vaccinated, especially following the third (booster) dose.

While vaccination provides less protection against contracting and transmitting the Omicron variant compared with earlier variants, it still provided some protection -especially after the booster dose.

One March study found explored data from some 2.2 million people in Qatar who'd received at least two doses of either the Moderna or Pfizer vaccine.

It found booster effectiveness against symptomatic Omicron was 49 per cent, compared with people who'd had only two doses, while effectiveness against symptomatic Delta was 86 per cent.

Importantly, though, it found boosting was still about 76 per cent effective at protecting Omicron-infected people against hospitalisation and death.

Nevertheless, Al-Aly's team said these results should be used to better prevent breakthrough infections in the first place instead of relying solely on vaccination, and to optimise care for affected people.

"Our results show that SARS-CoV-2 vaccination before infection only partially reduced the risk of death and post-acute sequelae," they said.

"Measures for the prevention of breakthrough infections are needed to most optimally reduce the risk of the long-term health consequences of SARS-CoV-2 infection."