For herd immunity to play a role in COVID-19 suppression, infected communities need to remain defended against the novel coronavirus for a consistent length of time.
A new study from the University of Amsterdam has potentially located said length of time at around six months.
The researchers monitored the antibody levels of 10 men between the ages of 27 and 40 for more than 35 years after they were infected with one of the four seasonal human coronaviruses. The participants were administered tests at either three or six months intervals.
Followup analysis determined an “alarmingly short duration of protective immunity to coronaviruses.”
More discreetly, the researchers noted: “Frequent reinfections at 12 months post-infection and substantial reduction in antibody levels as soon as six months post-infection. As protective immunity may be lost by six months post-infection, the prospect of reaching functional herd immunity by natural infection seems very unlikely.”
It’s important to clarify the biological differences between SARS-CoV-2 and the coronaviruses studied in the new report.
The authors themselves concede that the former has little in common with the rest apart from causing symptoms that are characteristic of the common cold.
Coronavirus denotes a family of RNA viruses. There are four main classifications that describe their ensuing diseases: Alpha, Beta, Gamma, and Delta. The first two infect human hosts.
Collectively, Alpha and Beta coronaviruses are responsible for 5-10% of all adult upper respiratory tract infections.
Where SARS and MERS have been subject to years of academic inspection, the virus driving our current pandemic is a uniquely sophisticated mutation that is only now beginning to yield consistent data sets.
Having said that, the ways in which SARS-CoV-2 is dissimilar from the pathogen family it belongs to do not negate the ways in which it may be revealed to be similar down the line.
Recent studies have determined undeniable similarities between some coronavirus strains.
“They all seem to induce a short-lasting immunity with rapid loss of antibodies. This may well be a general denominator for human coronaviruses,” the authors of the new paper wrote. “If SARS-CoV-2 will behave like a seasonal coronavirus in the future, a similar pattern may be expected.”
Immunity has value as far as countermeasures are concerned irrespective of its projected duration. Two independently conducted studies that used monkey models found little or no clinical disease in the animals following SARS-CoV-2 reinfection.
Upon reintroduction to the virus, the subjects developed antibodies so quickly they did not become discernibly sick even with traces of coronavirus attempting to penetrate their host cells.
If data confirms humans to evidence a similar pathology the herd immunity theory might be repurposed as an immunity antigen theory.
Harvesting antibodies will always be an important element of vaccination development and social distancing easing even if a communal bio-defense is never realized.
Just last week, Britain’s Health Secretary Matt Hancock announced that the government is initiating a “system of certifications” to enable people who have recovered from COVID-19 to resume certain activities based on the level of viral material still present in their bloodstream.
According to Mr. Hannock, antibody tests capable of delivering results in 20 minutes are currently being trialed on 4,000 patients.
“It’s that knowing you have these antibodies will help us understand more in the future if you are at lower risk of catching coronavirus, of dying from coronavirus and of transmitting coronavirus,” Hancock explained.
CW Headley is a reporter for the Ladders and can be reached at email@example.com.