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Parts of London and New York have already achieved 'substantial' immunity, Harvard epidemiologists say

People wear protective face masks in Times Square  - Getty Images North America 
People wear protective face masks in Times Square - Getty Images North America

Parts of London and New York have already achieved “substantial” immunity, with the threshold lower than previously thought, scientists have told the Telegraph.

The results of recent antibody testing has led experts to predict that some areas might be better insulated from any second surge of the coronavirus this winter.

“It’s reasonable to think that some local areas have a substantial amount of immunity. I think there are parts of New York and London which are there,” said Professor Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health. “It’s really noticeable in certain pockets, but it varies city block to block and we have to be careful when interpreting what it means.”

Experts point to new modelling which has used data on the spread of Covid-19 to suggest herd immunity - previously estimated to be upwards of 70 per cent - could be as low as 50 per cent, or even 43 per cent, as one study found.

Herd immunity is calculated from a reproductive number, referred to as R0, which is an indicator of how many people each infected person spreads the virus to.

Tom Britton, a mathematician at Stockholm University, calculated the threshold at 43 per cent.

“Our model shows how the disease-induced herd immunity level may be substantially lower than the classical herd immunity level derived from mathematical models,” he wrote in a report released this week. “Our application indicates a reduction of herd immunity from 60 per cent down to 43 per cent.”

Prof Hanage believes the threshold is “almost certainly” lower than 70 per cent, but not as low as 43 per cent.

“The 70 per cent threshold is the most naive and simple model. From what we have seen, I think we can drop it, but not by the amount that some have said,” the British scientist told The Telegraph.

“These cities have seen very large amounts of the disease, so you would hope that people in communities which were so severely affected back then will have gained enough immunity that they won’t be so severely hit next time around,” he said, referring to how hard areas recording high immunity rates may be hit this winter.

A march to honor people who have died during the coronavirus disease outbreak in Manhattan - REUTERS
A march to honor people who have died during the coronavirus disease outbreak in Manhattan - REUTERS

New York City has recorded some of the highest rates of immunity in the world.

Some 68 per cent of people who took antibody tests at a clinic in the Corona neighbourhood of Queens received positive results, while at another clinic in Jackson Heights, 56 per cent tested positive, according to figures released by healthcare company City MD last month.

New York City officials on Tuesday released data on more than 1.46 million coronavirus antibody test results, the largest sample to date.

Across the city, more than 27 per cent of those tested had positive antibody results. The borough with the highest rate was the Bronx, at 33 per cent. Manhattan had the lowest rate, at 19 per cent.

Corona, Queens, recorded a nearly 52 per cent positivity rate, which scientists say is likely to be more representative than City MD’s findings.

The neighbourhood has paid a high price, with 450 deaths recorded among its 110,000 residents.

Scientists did see some hope in the relatively low rate of new infections in New York City.

Its Covid-19 positive test rate on Saturday hit its lowest level recorded since the outbreak in March - at 0.69 per cent.

New York Gov. Andrew Cuomo speaks during a news conference - AP
New York Gov. Andrew Cuomo speaks during a news conference - AP

New York, once the epicentre of the virus in the US, was put under one of the country’s longest and strictest shutdowns.

Andrew Cuomo, the state’s governor, ordered mandatory mask wearing in public places in April. Restaurants and bars have slowly begun reopening, but only for outdoor dining.

Dr Dave Chokshi, New York City health commissioner, warned, however, against drawing too many conclusions from antibody rates and the decline in infections since there are still many outstanding questions about immunity.

Prof Hanage also cautioned that populations with high immunity levels should not be complacent.

“New York’s new case rate is some good news, but these static levels are not as a result of immunity. You’d expect it to be going down if that was the case,” he said.

“Even though it’s true the more immunity you have in a population the more bang you get for your buck when it comes to pharmaceutical intervention, if it isn't distributed there’s only so far it matters,” he said. “People move around, especially in urban areas. They can continue to contract it outside and bring it back to their communities.

“We can’t just go back to normal. Not yet.”