Two studies showed that vaccine protection appears to be waning among older people, especially among those 75 and older [Rachel Wisniewski/Reuters]

Atlanta, September 13 (RHC)-- The United States Centers for Disease Control and Prevention (CDC) has presented data showing unvaccinated people are four-and-a-half times more likely to contract COVID-19 and 11 times more likely to die from it than those fully vaccinated.

In a White House COVID-19 briefing, CDC Director Dr Rochelle Walensky said the data shows “vaccination works and will protect us from the severe complications of COVID-19”.

The studies involved more than 600,000 COVID-19 cases, hospitalisations and deaths in 13 states, and large cities from April through mid-July.

“Looking at cases over the past two months when the Delta variant was the predominant variant circulating in this country, those who were unvaccinated were about four-and-a-half times more likely to get COVID-19, over 10 times more likely to be hospitalised, and 11 times more likely to die from the disease,” Walensky said.

While protection remained strong against Delta, the study also confirmed an increase in milder COVID-19 infections among fully vaccinated people, which the authors said reflected “potential waning of vaccine-induced population immunity.”

Two other U.S. studies also found that COVID-19 vaccines offer strong protection against hospitalisation and death, even in the face of the highly transmissible Delta variant, but vaccine protection appears to be waning among older people, especially among those 75 and older.

U.S. data on hospitalisation from nine states during the period when the Delta variant was dominant also suggests that the Moderna vaccine was more effective at preventing hospitalisations among individuals of all ages than vaccines from Pfizer or Johnson & Johnson.

In that study of more than 32,000 visits to urgent care centres, emergency rooms and hospitals, Moderna’s vaccine was 95 percent effective at preventing hospitalisation compared with 80 percent for Pfizer and 60 percent for J&J.

Another study looked specifically at the performance of mRNA vaccines – such as the shots from Pfizer and Moderna – in patients at five Veterans Affairs medical centres, a racially diverse group made up largely of older male patients with higher rates of underlying disease.

Of the more than 1,000 COVID-19 hospitalisations in that study, researchers found that combined both vaccines were 86.8 percent effective against hospitalisation – even against the Delta variant. But vaccine effectiveness fell to 79.8 percent among veterans 65 and older.

In the third study, which looked at medical encounters in nine states, overall vaccine effectiveness remained high at 86 percent against hospitalisation and 82 percent against visits to the emergency room or an urgent care centre. However, vaccine effectiveness against hospitalisation was “significantly lower” among adults aged 75 and older, falling to 76 percent – the first time a drop had been observed in this data set.