Why the prejudice against tests for Covid-19 immunity?

Simon Thornley


Words: 1090

A curious phenomenon has developed in the race to beat Covid-19. Advisors to the government have recently become anti anti-bodies. Before I explain what that means, let me provide some context. While we’ve weathered the initial Covid-19 storm, we now have a more challenging set of questions ahead of us as we decide how far and fast to ease social restrictions and open our borders back up to the world.

One of the most critical is: just how widespread is this virus? If, as the Government’s advisors believe, it’s a case of ‘what you see is what you get’, then our options are limited. But if, as we are seeing around the world, the virus has spread through far more of our population than we are aware, then that changes everything. All of a sudden, we need to radically re-think whether our control measures make sense. The genetic test that we are relying on can tell us if the virus is active in the here and now. That is the focus of the daily case counts. These tests are accurate, and the best for diagnosing cases, but they don’t give us a complete picture.

In almost all infectious diseases, antibody tests play a crucial role in determining who is protected from the germ and who is not. They tell us that a virus or germ has been and gone. They are the fingerprints that the virus leaves behind, and allow us to be better prepared for the next encounter. For Covid-19, we may not otherwise know we have met and dispatched the virus, since not all of us develop symptoms. In Iceland, of the few areas of the world a survey was carried out, rather than only testing sick people, 1% of the population tested positive, but half all these positives were perfectly well. It is now clear that just because we don’t have a fever, runny nose or cough, it doesn’t mean we haven’t seen the virus. For this reason, we simply cannot rely on genetic tests from people with symptoms to tell us how far the virus has spread. To really get a handle on how many of us have seen a virus, we need to not only count active cases, but start measuring people who have seen the virus before with antibodies.

New Zealand is now at a cross-roads. We have two explanations for our results. Professor Michael Baker, one of the main experts advising the government, has expressed that antibody tests “would be a waste of time and resources” since a “vanishingly small” proportion of the population have been exposed. Through Baker’s eyes, the lockdown was astonishingly effective, quashing the virus, while leaving all except the one and a half thousand or so cases sitting ducks waiting for infection to strike. We had better live in fear and shut down the borders hard. This narrative goes with the elimination story. So much for our travel and tourist industry. Sorry Rotorua and Queenstown, we have laid you on the altar as a casualty on the path to vanquishing the virus.

Another explanation for the rise and fall of cases in New Zealand is from growing immunity, rather than from the lockdown. The cases of infection rise as the virus encounters more susceptible people. This is great for the virus until it encounters people who have seen the virus before. Their bodies have wised up, thanks to our miracle antibody factories, and the virus sees the door is shut. Some may not even need antibodies. The innate and cellular immune system, like a razor wire fence, may keep the virus out before the soldier-like antibodies need to be enlisted.

Immunity from other viruses is also likely to play a part. A recent study estimated that half of people who haven’t seen the novel virus before, have T cells that react against it which are primarily directed against ‘common cold’ coronaviruses. The virus looks elsewhere, but the door is shut with the next person, and the next, and it soon has nowhere to go. This has been the way we have defeated almost every other lung virus of equivalent severity to Covid-19 in the past.

Now critics will say there are holes in this immunity theory. If that had really happened, we should have seen chocka intensive care units like in Italy. Well, we may have, or we may not. It is clear that New Zealand is not Milan, London and New York, as we would like to believe. We are simply nowhere near as population-dense as these metropolises.

Surely we would have noticed excess deaths? Or excess people coming to hospital with influenza-like symptoms? Since the deaths from Covid-19 are about the same average age as our life expectancy, we may not have noticed. If we hadn’t tested for it, we would have probably not batted an eyelid. We would have put the death down to the growing list of diseases that were likely to have afflicted the deceased. And it is not as if Covid-19 gives a unique clinical presentation. As a former hospital doctor, I know only too well that patients who present with flu-like illness are extremely common. A recent positive test in a French patient well before the ‘official’ epidemic occurred support this theory of widespread infection.

Teasing out which of these two beliefs to follow is now critical. History may help. In recent memory, a story played out according to the widespread immunity theory. We strongly believed that H1N1 was a killer virus, rapidly spreading out of Mexico. The death rate was astonishingly high initially. The clamour to ‘stamp out’ the virus in New Zealand was long and loud. It was, at least, until needles were put in veins, and antibodies were present in 47% percent of some age groups. These tests established that many New Zealanders had seen the virus and the chorus to defeat the virus lost its stuffing.

Evidence from other countries supports the idea of widespread immunity. The very small secondary overseas outbreaks, such as in China and the Australian state of Victoria are further evidence that widespread immunity is growing. If, instead, immunity were sparse, we should expect many further large outbreaks. Other commentators have condemned the low accuracy of Covid-19 tests, however, Roche now has produced a test that has sensitivity and specificity values approaching perfection (100%) that has now got widespread acceptance in Europe. Not even many of our established antibody tests have achieved this.

The philosopher George Santayana reasoned, “those who cannot remember the past are condemned to repeat it.” At this crucial juncture, history indicates that the value of antibody tests and the idea of growing immunity cannot be so easily dismissed. If the virus is more widespread than the genetic tests indicate, we need to urgently reconsider whether or not border closures and social restrictions are really worthwhile.