Science of uncertainty: Gov’t adviser on why this COVID wave is so hard to predict
Prof. Ran Balicer says current spike reflects waning immunity, a new variant and summer AC use — but widespread unreported home testing means we don’t know yet how severe it’ll be
Nathan Jeffay is The Times of Israel's health and science correspondent
Scientists simply don’t have the tools to accurately predict how Israel’s sixth coronavirus wave will pan out, according to a top government adviser.
Epidemiologist Prof. Ran Balicer, chair of Israel’s National Expert Advisory Team on the country’s COVID-19 response, told The Times of Israel that doctors don’t know how much serious illness to expect, as erratic testing patterns mean the data has limited use.
This is especially problematic as the new BA.5 variant accounts for around half of Israel’s new cases. Experts say it’s too soon to understand the ability of this variant to cause serious illness.
Balicer and other top doctors believe that large numbers of infections are going unreported, which he says makes it impossible to know what percentage of COVID-19 cases today result in serious illness. This is partly due to the widespread availability of reliable home tests that cause many people to diagnose themselves and isolate, without reporting the results. In turn, this undermines the ability to analyze how hard the new wave will hit hospitals.
“In every new wave and every new variant there is a substantial period of uncertainty about the basic traits of the new variant and therefore the impact of an ensuing wave,” Balicer told The Times of Israel. “This is actually prolonged now compared with earlier waves because of a lack of reliable data on true infection rates.
“Today, many infections go unreported. [Institutional] testing is less accessible than it was, and requirements regarding when to test are less clear to people. Many people get infected and don’t take an institutional test, just a home antigen test. This makes it very hard to know what percentage of people with COVID-19 are hospitalized, and therefore to compare the rates of serious illness with previous variants. All of this makes it very difficult to anticipate how this new surge may pan out.”
This effect is exacerbated by the fact that people have widely varying degrees of immunity, having received different numbers of vaccine shots and having been infected previously by several variants, making it even harder to anticipate how a renewed outbreak may impact society.
Balicer spoke in a wide-ranging interview, conducted as the average number of new daily cases — based on a moving weekly average — has hit 9,800, compared to less than 2,000 a month ago. The number of serious cases has more than doubled over the last two weeks, and now stands at 285.
Balicer said that the rise in cases hasn’t come as a surprise, in view of waning immunity, a new variant and a tendency to shut windows in response to summer heat.
“COVID-19 and some other infectious diseases are characterized by patterns of surges and oscillations,” Balicer noted. “The current increase can be attributed to several factors coming together. One is gradually waning immunity from the Omicron surge that we saw earlier this year and the continuously waning immunity from past vaccination campaigns. We also have the emergence of new strains, in this case BA.5, which may be a contributing factor.
“It’s too early to say what the characteristics of BA.5 are in terms of evading immunity from previous vaccination and illness — that’s still open-ended — but it could be contributing to virus spread. The third factor is the summer and the tendency of people to spend time in air-conditioned rooms with windows closed, which means a lack of ventilation. This can also impact case numbers. We saw a surge at this time of year throughout the pandemic, possibly in part due to this reason.”
Israel’s winter coronavirus wave, which dominated late 2021 and the start of 2022, caused widespread infection, and it isn’t clear whether immunity among recovered patients will protect them at this point from the new wave.
Balicer said that in many cases, the virus will be able to break through immunity acquired in the winter wave. However, the illness could well be significantly lightened as a result of residual immunity.
“The population in Israel currently has residual long-term protection from previous vaccination campaigns, meaning three doses for adults and four for high-risk [groups]. There is also boosted immunity for many who were recently infected,” he said.
“While it seems that the protection against getting infected lasts only for a couple of months before massively waning, protection against serious illness seems to last, at least partly, for many months. And so, while we see an increase in serious cases right now and while it’s quite possible numbers will increase further, our data suggests residual protection continues to exist. The potential for a wave of severe infection now is very real, but it may be partially curbed by residual immunity in the population.”
Despite concerns about the current wave, Balicer said that there are no plans to offer fifth vaccine doses, even to the elderly or at-risk populations. This is because decisions to introduce new vaccine doses are a balancing act between possible safety risks and urgency, and Balicer said there just isn’t a sense of urgency at the moment.
“We have been asked about whether we will consider a fifth dose, and such a recommendation wasn’t made at this point due to lack of evidence about effectiveness and safety at this specific setting,” he said. “We are quite uneasy about taking such decisions unless facing an imminent public health emergency. In the past, decisions were made in Israel based on partial evidence that was later shown to be correct in retrospect and vindicated as scientifically accurate. You make decisions with a lack of existing data when the alternative of watchful waiting is clearly and dramatically worse — and that is not the case now.”
One change that may be in the cards relates to masks: the reintroduction of compulsory masks indoors is being discussed among decision-makers.
“There are discussions among the experts advising the Health Ministry over whether there should be a mask mandate,” Balicer said. “This is something that could be considered. The practical difference stemming from the current recommendation and a mandate is the perceived legitimacy of someone who is at risk of severe COVID-19 going into a room and requesting others to wear masks, regardless of their personal preference. Public willingness to agree could be higher if there is a mask mandate.”
Asked whether people can conclude that “residual immunity” will mean that the current wave is milder than the winter wave — and that by extension the health system won’t be overwhelmed — Balicer said: “This does make intuitive sense, but we cannot be sure at this point. There are still open-ended questions regarding the severe illness rates caused by BA.5 and its ability to evade past immunity.
“So we must still keep a close watch on how the severe illness rates unfold in the coming days and weeks. And, while perhaps not overwhelming [the health system], the burden of serious cases during the Omicron wave in early 2022 was high and painful, and we should aim not to repeat it.”
