Mass inoculation: Spain, UK near achieving herd immunity

ISLAMABAD: 'Herd immunity', also known as 'population immunity', is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection.

On Monday, the Spanish prime minister said Spain is “just 100 days away from reaching herd immunity” to COVID-19, while the UK vaccine taskforce said that they would achieve it by August.

Vaccines train our immune systems to create proteins that fight disease, known as ‘antibodies’, just as would happen when we are exposed to a disease but – crucially – vaccines work without making us sick. Vaccinated people are protected from getting the disease in question and passing on the pathogen, breaking any chains of transmission.

To safely achieve herd immunity against COVID-19, a substantial proportion of a population would need to be vaccinated, lowering the overall amount of virus able to spread in the whole population. .

The percentage of people who need to be immune in order to achieve herd immunity varies with each disease. For example, herd immunity against measles requires about 95% of a population to be vaccinated. The remaining 5% will be protected by the fact that measles will not spread among those who are vaccinated. For polio, the threshold is about 80%. The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritised for vaccination, and other factors.

Achieving herd immunity with safe and effective vaccines makes diseases rarer and saves lives. Attempts to reach ‘herd immunity’ through exposing people to a virus are scientifically problematic and unethical. Letting COVID-19 spread through populations, of any age or health status will lead to unnecessary infections, suffering and death.

Spanish PM Pedro Sanchez during a news conference in Greece asserted once 70% of the population is vaccinated, the country will have achieved that goal. “The data invite optimism. One-third of the adult population in Spain has already received one dose, and half of that group has been fully vaccinated,” Sanchez told.

“Today, we’ll reach the goal of 6 million people fully vaccinated,” he continued. This is the clearest timeframe laid out yet for Spaniards, putting the tantalizing target of herd immunity in mid-August.

Previously, Spanish officials had pledged to reach the goal by “the end of summer.” Spain’s vaccination campaign has accelerated in recent weeks. On Thursday, a record 573,014 people received jabs.

If the vaccination campaign speeds up only slightly and vaccine acceptance remains strong, 70% of the adult population could be immune to the virus within little more than three months.

Yet experts are still split over when herd immunity, which is achieved when enough people are immune to an infectious disease to protect even those who are not immune, could kick in for COVID-19. At the beginning of the pandemic, many experts estimated that the herd immunity target would be reached once 60-70% of the population had become immune to COVID-19.

COVID will "no longer be circulating in the UK by August", the outgoing chief of the UK’s vaccine taskforce has said. Clive Dix, who took over the role in December and stepped down some days ago, said it was his belief the UK will have a population protected from COVID this summer.

He told the Daily Telegraph: "We’ll have probably protected the population from all the variants that are known. "We’ll be safe over the coming winter," he added. His comments come as more than 50 million doses of a COVID vaccine have been distributed in the UK, 16.7 million of which are second doses, according to government figures.