Herd immunity won't work without a vaccine, Spanish scientists find

In the case of most of the common diseases caused by airborne virii, including by other types of Coronavirus itself – one strain of Coronavirus is responsible for the common cold – vaccinating the most vulnerable members of the population largely prevents mass contagion and, in the case of some contagious or infectious diseases for which vaccinations have been invented, their prevalence has been wiped out altogether in the western world.

Diphtheria, smallpox, and even more recent conditions such as whooping cough are almost extinct now because of those likely to catch them or who would suffer worse if they did being inoculated, and unvaccinated patients who contract them being healthy enough to recover quickly with few or no side-effects, their bodies developing an immunity to them as a result.

With no vaccination as yet available for Covid-19, 'herd immunity' can only be achieved through those catching it developing antibodies that stop them getting infected again, meaning they cannot pass it onto anyone else.

But Spanish scientists have been carrying out an extensive nationwide study into seroprevalencia – the prevalence of antibodies within the population – and have concluded that around 95% of those tested have not acquired an immunity to the virus.

They tested over 60,000 volunteers who had been exposed to the Coronavirus, according to the results of the experiment published in science journal The Lancet, and discovered antibodies in only around 3,000 of them.

For 'herd immunity' to work, between seven and nine in 10 members of the population needs to be immune to a condition.

Although immunity was greater in parts of the country which had been ravaged by Covid-19 – such as Madrid – in other areas, including the east coast, which had only a minimal, often barely anecdotal, incidence, immunity was found to be lower than 3%.

This means those areas which have escaped the worst of the devastation may in fact now be among the most fertile territories for a further outbreak to take hold.

Even in parts of the country torn apart by the pandemic, immunity was found to be in such a reduced minority as to be considered practically absent in scientific terms.

The report in The Lancet says the only way of achieving 'herd immunity', or inmunidad de rebaño as it is known in Spanish, would be to allow the SARS-CoV-2 to reproduce unchecked among the public, bringing 'collateral of many deaths' in the most vulnerable members of society, and causing absolute chaos in healthcare departments nationwide.

Said to be the biggest seroprevalencia study in Europe, the results show that the only possible way of containing the SARS-CoV-2 virus in the absence of a widely-available and effective vaccine is through social distancing, stringent testing, and immediate isolation of anyone who displays symptoms or shows up positive – which do not, necessarily, always come together.

Cases of Covid-19 in nursing homes since the end of Spain's lockdown have been asymptomatic in 70% of patients, and among the general public, 60%.

Whilst this means that those who have caught the disease are probably not facing any immediate life or health risk, it does mean that they can pass it onto potentially hundreds of people at a time, given that they are unaware they are carriers.

Exposure to Covid-19 may or may not result in immunity – given that patients all over the world have recovered and then caught it again – but the very reduced presence of antibodies found in tests shows that the overwhelming majority of the population has not been in contact with the virus, even in areas with hundreds or even thousands of cases reported.

Also, the study in Spain found that immunity to Covid-19, where it exists, is not permanent and tends to diminish after a couple of months.

This means a cured and immune patient may be safe for the moment, but if autumn brings a fresh outbreak, they may be just as much at risk as anyone else of catching the disease.

At present, although most of Spain has not reported any significant numbers of new cases for weeks – for example, in the north of the province of Alicante, one new diagnosis was made this week after more than 40 days with none at all – and daily death rates have been in single figures with up to a week at a time passing with no fatalities, some localised outbreaks have caused concern.

Parts of Galicia have been put back into semi-lockdown after a spike in cases, around half of which were in the province of Lugo, and the Segrià district of the province of Lleida, Catalunya has returned to partial confinement, with nobody permitted to enter it from outside and its residents banned from leaving.

Pockets in almost every region have been reported, but as the World Health Organisation predicted earlier this year, these second outbreaks are localised.

Also, Spain is now immediately testing anyone, residents and tourists alike, who displays one or more symptoms or who has been in contact with an active case, and isolating 'suspects' straight away.

Airport arrivals are required to fill in a form, leave their contact details, and will have their temperature taken.

Even some shops and other high-street businesses are doing likewise with all customers, in addition to limiting numbers of people on the premises and making it obligatory for those who enter to wear masks and use hand sanitiser.