People line up to test for coronavirus disease (COVID-19) in a mobile test car on August 27, 2021 in New York City.

Brendan McDermid | Reuters

The US goes into Labor Day weekend with just over four times as many Covid-19 cases and more than twice as many hospital admissions as it did at that time last year – despite 62% of the American population having been vaccinated with at least one dose.

The US and the world are nowhere near where health officials hoped and thought we would be 20 months after the pandemic – and more than eight months after vaccines came out with efficacy rates of around 95%.

Although the outbreak is significantly worse than 2020 on most measures, the delta variant, vaccines, and open schools make it difficult to predict how the pandemic will develop, doctors and scientists say.

“Right now there is a lot more uncertainty. The dynamic interaction between variants and vaccine and especially unvaccinated persons and the type of game changer of the Delta variant leads to a lot of uncertainty as to what the case will bring, “said Dr. Barbara Taylor, Assistant Dean and Infectious Disease Specialist at the University of Texas Health Science Center at San Antonio.

The Centers for Disease Control and Prevention has advised unvaccinated Americans against traveling over the holiday weekend because they feared the celebrations could trigger further spikes in cases.

On the way to Labor Day 2020, the U.S. saw a summer spike with the average daily cases spike in July from about 67,000 per day to an average of just over 41,000 new cases per day in the week leading up to Labor Day, data released by the Johns Hopkins University shows. New cases this week are at their highest level since January, averaging 166,000 per day for the past seven days.

However, the number of new cases is increasing much more slowly than in recent weeks, and many scientists are predicting that they will soon decline. New cases rose 7% last week, nearly a third of the seven-day jump from 26% just three weeks ago, the data said.

“It is true that cases, hospital admissions and deaths are higher than last Labor Day, especially in most southern states,” said Lawrence Gostin, director of the World Health Organization’s Collaborating Center on National and Global Health Law. “That was very surprising because we now have highly effective vaccines.”

However, the effectiveness of all three US-approved vaccines – Pfizer, Moderna, and Johnson & Johnson – have declined since they were launched. Scientists have found that protection wears off over time. The highly contagious Delta variant is also a game changer. It spreads more easily and quickly than other variants, according to the CDC, and infects both unvaccinated and vaccinated people.

The viral load in the nasal cavity is so high, an estimated 1,000 times higher than other strains, that scientists in Australia say they followed a case where a man became infected with just 5 to 10 seconds of exposure. The small fraction of fully vaccinated people who get Covid, even an asymptomatic case, are just as capable of spreading it as unvaccinated people, officials warned. The Delta variant now accounts for 99% of all newly sequenced cases in the United States

“The Delta variant, as we’ve seen with the development of Covid-19 over the past year and a half, continues to curve us, and I think the best advice is to be careful and careful,” Dr. Nusheen Ameenuddin, a Mayo Clinic pediatrician said in an interview.

The good news is that Delta seems to be on its way in the US and there are no more new people to infect as vaccination rates rise and others gain natural immunity after recovering from the virus, doctors and scientists say.

The number of new admissions to hospitals has finally changed after weeks of steady growth, with the seven-day average of daily admissions dropping 1.7% over the past week, CDC data shows. Still, more than 100,000 Americans are currently being hospitalized, compared to about 41,000 the same week a year ago, according to the Department of Health and Human Services, up from levels as of late January this year.

The big question is: how long does immunity last? Studies show that the vaccines’ effectiveness wears off about two months after the second vaccination and then really loses protection five to eight months after the full vaccination, US officials say.

“We can see periodic waves of this until there is adequate protection at the community level, and hopefully it will be through vaccination rather than recovery from natural infection,” said Dr. Isaac Bogoch, an infectious disease doctor at the University of Toronto. “I know we all want the pandemic to be over, but it’s not. We’re closer to the end in countries with access to vaccination, but it’s not over yet. “