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Published online 7 May 2020
TB vaccine immune boost shields newborns against sepsis
The tuberculosis vaccine also boosts newborn immunity against sepsis, an often fatal infection, by ramping up immune cell production in the spleen.
The BCG vaccine, primarily used against tuberculosis, can also shield newborns against sepsis by rapidly accelerating a process that produces immune cells called neutrophils. The finding1 , by an international team of researchers, including two in Qatar, explains the results of a previous study2 that found that BCG vaccination shortly after birth significantly reduced fatalities from sepsis, a severe infection that causes inflammation throughout the body and organ failure.
To understand the BCG vaccine’s protective effect, the researchers vaccinated newborn mice and then induced sepsis in them three days later. They found that the vaccine markedly improved their survival.
The main mechanism of this improvement was increased production of neutrophils by the spleen following vaccination. The vaccine also led to a reduction in the production of potentially harmful proteins that trigger inflammation. This led to a reduction in the bacterial load in blood and various organs 24 hours into sepsis. The vaccine had similar protective effects in human newborns, who showed an increased number of neutrophils in their peripheral blood.
The vaccine’s protective effect waned in mice within two weeks. It also failed to protect mice that were vaccinated later, at six weeks of age. Additionally, it did not protect human newborns already diagnosed with sepsis.
"Given that most newborn deaths occur within days of birth, the most effective way to prevent sepsis would be to give the BCG vaccine at birth," says Nelly Amenyogbe of the Telethon Kids Institute, Australia. "Delaying the vaccination may still confer some protection against sepsis, but many of the at-risk newborns that would have benefitted most would have succumbed to disease already."
“This study has implications for BCG vaccine policy, as it adds to the growing evidence that BCG is far more active than being a specific vaccine against tuberculosis,” says Nigel Curtis, a specialist in paediatric infectious diseases at the Royal Children’s Hospital, Australia, who was not involved in the study. The vaccine enhances immunity, which can lead to increased protection against a wide range of infections, he explains.