A Washington D.C.-based internist and former Harvard Medical School faculty member has claimed the idea that herd immunity may slow the coronavirus pandemic is “wishful thinking” after a 50-year-old patient was infected for a second time with COVID-19.
“During his first infection, my patient experienced a mild cough and sore throat,” Dr. Clay Ackerly explained in an opinion piece for Vox. “His second infection, in contrast, was marked by a high fever, shortness of breath, and hypoxia, resulting in multiple trips to the hospital.
“It is possible, but unlikely, that my patient had a single infection that lasted three months,” Dr. Ackerly added. “Some Covid-19 patients (now dubbed ‘long haulers’) do appear to suffer persistent infections and symptoms.
“My patient, however, cleared his infection — he had two negative PCR tests after his first infection — and felt healthy for nearly six weeks.”
Typically, experts estimate that between 70 and 90 percent of a population must be immune to a contagious disease to achieve herd immunity — whether through vaccination or other exposure to an infection.
However, a recent study in Spain, one of the countries hardest-hit by the pandemic, found just five percent of those surveyed had coronavirus antibodies. On a regional basis, the percentage varied from fewer than three percent in coastal regions to more than 10 percent in areas around Madrid.
Herd immunity is when a virus can no longer spread easily because enough people are immune to it. That lowers the chances of the virus jumping from person to person and reaching those who haven’t been infected yet.
People can become immune to certain viruses after surviving infection or being vaccinated. Typically, at least 70 percent of a population must be immune to achieve herd immunity. But how long immunity lasts varies depending on the virus, and it’s not yet known how long COVID-19 survivors might have that protection.
“Infection tends to give you the best-case scenario for an antibody response, so if your infection is giving you antibody levels that wane in two to three months, the vaccine will potentially do the same thing,” Dr. Katie Doores, who authored the study, told the Guardian. “People may need boosting and one shot might not be sufficient.”
Ackerly concluded his piece by warning that if his patient is not … an exception but instead proves the rule, then many people could catch Covid-19 more than once, and with unpredictable severity.”
“Natural herd immunity is almost certainly beyond our grasp,” he warned. “We cannot place our hopes on it.