Vaccination efforts are working, if the latest data is anything to go by.

Every week, Public Health England (PHE) releases a report, which details information like where the virus is spreading and among which age groups.

It also includes data on seropositivity in the population in England – and it’s this that’s showing positive signs. A person is ‘seropositive’ when specific Covid-19 antibodies, which help the immune system fight the virus, show in their blood.

Data suggests there’s been a “large rise” in seropositivity in the first four weeks of 2021, increasing from 12.1% of the population at the end of 2020, to 20.5%.

While this can be attributed to the increased transmission we’ve witnessed – meaning lots of people have naturally made their own antibodies after becoming ill – data shows the over-70s group are experiencing a notable rise. PHE believes this could also be down to the vaccines being rolled out.

Seropositivity increased across all age groups, “but most notably in 70-84 year olds”, the report states. Seropositivity in this group has risen from from 4.1% at the end of December to 9.7% in January 2021.

“The most recent increase in seropositivity in those aged 70- 84 is likely due to a combination of increased transmission and vaccination that started during December 2020,” reads the report.

The largest rise in seropositivity was seen in those aged 17-29 years old, with prevalence increasing from 11.4% to 17.5%.

Professor Paul Hunter, from the Norwich School of Medicine at the University of East Anglia, tells HuffPost UK that although the prevalence in the 70+ age groups has increased more than in most other age groups, “it’s only when you compare this with the PCR prevalence published by the ONS Covid-19 infection survey that the significance of this increased seroprevalence becomes clear.”

The ONS data shows of all age groups in England, those aged 70+ are now least likely to test positive for the virus. “From the ONS report, no firm conclusions about the impact of vaccination can be drawn,” continues Prof Hunter, “but it is clear that during most of January, infection rates were lower in the 70+ age group compared to all other age groups. 

“So for antibody prevalence to have increased in this older age group as much as it did, immunisation must have played an important role.”

Prof Hunter suggests antibody prevalence will “increase substantially” in the older age groups over the next few weeks. 

Professor Richard Tedder, senior research investigator in medical virology at Imperial College London, says the observation that the elderly age group are increasingly seropositive is “comforting” and indicates “a demonstrable impact of the government’s targeted immunisation for the elderly”. 

He did add however that it’s important “to be careful in extrapolating from a serological reactivity induced by immunisation to actual protection against infection and resulting protection against illness”.

“That said these observations are important and ‘pointing’ in the right direction.  It also demonstrates the value of undertaking post immunisation antibody testing as a routine exercise,” he tells HuffPost UK.

As well as increased antibodies in the older age groups, there’s also been a large fall in hospital admissions among those aged 85 years and over in the week ending January 31, when 206.4 per 100,000 people were admitted to hospital. This was down from 282 per 100,000 the week before.

Near the end of January, deaths were still increasing in all age groups bar those aged one and under – but it’s likely these people became ill over the Christmas period. There can be a lag of around three or four weeks between diagnosis and death, so we might not see an impact on the death rate for a few more weeks.

Hospital admissions and deaths have consistently been highest among those aged 65 and over. Of more than 96,900 deaths involving Covid-19 in England to date, almost 90% were among people aged 65 years and over.

The government hopes to provide 15 million people in the top four priority groups with a first dose of the Covid-19 vaccine by February 15.

More than 13 million people have already been vaccinated with their first dose.