It seemed that the coronavirus pandemic was on its way out due to widespread vaccination efforts with states implementing temporary lockdowns and restrictions to curb small outbreaks of the virus. However, recent spikes in infections across disparate parts of the world have proven otherwise.

Health experts across the globe worry that, with the upcoming winter, the number of COVID-19 infections will increase dramatically and even the widespread inoculations will not able to stop the deadly virus. Although European countries were the first to start vaccination programs for their citizens earlier last year, many nations have faced an unprecedented rise in infections recently. This follows the lifting of some vital restrictions, which together with inoculations were holding the COVID-19 pandemic in check.

Great Britain, its hospitals and its COVID-19 strategy are under the microscope as the country enters the dangerous winter period while accounting for almost a tenth of the world's newly recorded infections. The United Kingdom's Prime Minister Boris Johnson outpaced many governments by ending England's pandemic restrictions in one broad stroke in July, betting that the National Health Service (NHS ) would be able to handle the strain after a successful vaccination campaign. Some front-line healthcare workers, virologists and pandemic modelers aren't so confident.

Even though COVID-19 hospitalizations are far lower than a year ago, experts say pressures will be compounded by other winter viruses previously halted by lockdowns, as well as vaccine immunity fading and a backlog of treatment for other conditions.

"I wouldn't take those warnings from NHS staff lightly at all," said Imperial College London's Pablo Perez Guzman, who works on one of three models used to advise the government. "That is an amount of pressure that the health system might struggle to cope with. Definitely."

While Britain's new cases have persisted above 30,000 a day since early September, vaccines have driven deaths from COVID-19 down by about 90% compared to January levels. Yet, if the concerns of Perez Guzman and eight other specialists interviewed by Reuters prove well-founded, Johnson may be forced to implement his "Plan B" aimed at protecting the NHS from "unsustainable pressure," involving mask mandates, vaccine passes and work-from-home orders. More economically damaging restrictions are not out of the question, scientists say. The government said its focus was on administering vaccine boosters and inoculating 12 to 15-year-olds. It said the data didn't yet show that Plan B was necessary, though the contingency has been held at the ready.

Stephen Griffin, a virologist at the University of Leeds, predicted that the state-funded NHS would "get overwhelmed again."

"Even though COVID isn't responsible for as many of the ICU places as it has been in the past, it's still around a third of them, and that's going up," he told Reuters. "I don't know how they're expecting NHS staff to cope, mentally and physically."

Others leaders considering their own tactics are closely watching this global test case of whether vaccination is enough to handle the highly transmissible delta variant of the virus. Italian Prime Minister Mario Draghi said last month that he believed Britain had erred by opening up on July 19, a lesson that the world could not exit the crisis "in an instant."

"The United Kingdom, which was one of the countries that carried out the vaccination campaign with great speed, abandoning all caution, is now faced with about 50,000 daily infections and 200 deaths yesterday," he told lawmakers. "Even in the exit it will be necessary to exit gradually."

Data for hospitals in England – home to more than 80% of the U.K. population – shows that the cumulative pressures are already straining the system, even though the 1,000 new COVID-19 admissions each day are lower than the 1,500 seen a year ago and the 4,000 in January. And winter is coming. Hospital accident and emergency departments treated 1.39 million patients in September, the highest number for any month on record. About a quarter of those waited more than four hours for treatment – the highest proportion since at least 2010.

While Britain isn't the only country confronting the challenges of COVID-19 while rebooting its health system, it was stretched long before the pandemic, with one of the lowest rates of hospital beds per capita in Europe. It has been hardest hit in the region by the disease with 140,000 deaths.

Johnson's exit strategy diverges from many other big economies, including Germany, France, Italy and Israel, which have either retained some basic COVID-19 measures like mask mandates or reintroduced them in response to rising cases. Masks are still asked for in certain settings in England, including on public transport and when meeting infrequent contacts in enclosed spaces, but there is no legal requirement. As a result, mask usage has declined significantly, government scientific advisers said in October.

"We do not understand why the government has removed mandatory mask wearing in transport and in indoor settings like shops because that doesn't actually stop the economy functioning – but it would reduce infection," Chaand Nagpaul, chair of the British Medical Association (BMA) council, told Reuters. "The government clearly believe these simple measures do make a difference, yet they're failing to act by not making these a requirement. Without other preventative measures put in place now, the challenges coming our way could go from being achievable to totally insurmountable."

Meanwhile in France, face masks will once again become obligatory in schools in 39 regional departments where COVID-19 cases have crossed the alert threshold, a government spokesperson said Wednesday. As schools in the country reopen on Nov. 8 following brief holidays, the mask rule will be reimposed for primary schools amid concerns over daily new cases, Gabriel Attal said at the weekly press conference, according to Anadolu Agency (AA). The 39 departments are in addition to the 22 departments where masks were declared compulsory last month, taking the total to 61, or nearly half of the French territory. Attal said in the concerned 39 departments, the incidence rate is above 50 cases per week per 100,000 inhabitants and therefore masks in primary schools will be back again.

According to the school protocol announced by French Ministry of Education, if a department has a low circulation of the virus and the incidence rate is less than 50 cases per 100,000 inhabitants for five consecutive days, then primary school students do not need to mask up. While the number of daily new cases is significantly lower, Attal said as soon as the situation deteriorates, health measures that were lifted will be reactivated. According to the latest Health Ministry data, there are 10,050 new cases, 39 fatalities and 6,764 COVID-19 patients admitted in hospitals.

Britain has about 40,000 daily cases of COVID-19, according to the latest seven-day average. That total is second only to the roughly 74,000 a day in the United States, which has five times more people. Nonetheless, the situation is better than some projected when Johnson ended England's COVID-19 restrictions. At the time, Health Secretary Sajid Javid warned that cases could hit 100,000 cases a day by the end of the summer. Instead, they peaked just below 55,000 cases a day two days before restrictions were lifted, falling away with the end of the Euro 2020 soccer championships and the start of the summer holidays. But daily case numbers never fell below 20,000 a day, and there are over 9,000 patients in hospitals even before the colder winter months ratchet up pressure on the health system. Javid said last month that infections could still hit 100,000 a day during winter.

England's deputy chief medical officer warned on Wednesday that Christmas may be difficult as the COVID-19 pandemic is not over, urging people to behave with caution and come forward for booster shots. "Too many people believe that this pandemic is now over. I personally feel there are some hard months to come in the winter and it is not over," Jonathan Van-Tam told BBC TV, adding that behavior and uptake of booster shots would determine the severity. "Christmas and indeed all of the darker winter months are potentially going to be problematic."

Hesitancy among citizens in getting a vaccine shot has brought Ukraine and its neighbor Russia to the highest figures of COVID-19 cases, with Kyiv announcing Thursday that the total number of COVID-19 cases in the country has exceeded 3 million with more than 70,000 deaths. According to the Ukrainian Health Ministry, it had registered a record daily high of 27,377 new coronavirus infections over the past 24 hours, exceeding the previous high of 26,870 on Oct. 29. Ministry data also showed 699 new coronavirus-related deaths.

Ukraine has registered record-high rates of new cases and deaths from the coronavirus in recent weeks, and the government has imposed strict lockdown restrictions to curb new infections. Several thousand people blocked traffic in the center of the Ukrainian capital Kyiv on Wednesday in a protest against coronavirus restrictions and mandatory vaccinations. Vaccines have become mandatory for some state workers, and in "red" zone areas including Kyiv, only vaccinated people or those with negative COVID-19 test results are allowed into restaurants, gyms and on public transport. Russia reported on Thursday a record 40,217 new coronavirus cases and over 1,900 deaths as non-essential services, including retail outlets, restaurants, sporting and entertainment venues are to remain closed in Moscow until Nov. 7.

The health ministers of Germany's 16 states began a two-day meeting in Lindau, on the shores of Lake Constance, on Thursday as rising coronavirus cases prompted alarm. Conference host Bavaria called for booster shots of the vaccine to be made available to all residents.

Statistics from the Robert Koch Institute (RKI) on Thursday put the proportion of those older than 18 and fully vaccinated at 77.4%, with the overall figure at 66.8% of the population. The number of coronavirus infections recorded in Germany within a 24-hour period hit a new all-time high of 33,949 on Thursday, surpassing by 172 the figure recorded on December 18. The figure was sharply up from the 28,037 cases posted a week ago.

In China, authorities are struggling with most widespread COVID-19 outbreak since the first wave of infections hit the country from Wuhan in 2019. According to the National Health Commission (NHC), the outbreak started on Oct. 16 when members of a fully-vaccinated tour group from Shanghai tested positive for the virus. This outbreak has spread across 19 of China's 31 provinces.

Chinese authorities immediately ordered mass testing, snap lockdowns and quarantines as well as vigilant surveillance and restrictions on international trips. The country's capital Beijing applied some entry restrictions into the city and placed rule-breakers in criminal detention as punishment for not obeying. The state-run newspaper The Global Times said Wednesday that nearly 500 cases of coronavirus have been recorded nationwide since the mid-October outbreak. While the figure may seem small for Western countries, hundreds of infections in China have rocked its "zero-COVID approach," which hopes to contain the virus completely within Chinese borders. It insists that most people arriving from outside the mainland be quarantined for weeks, regardless of their vaccination status.

In the other parts of the world, celebrations and national events have triggered concerns among health experts who advised against large crowds. Indians across the country began celebrating Diwali, the Hindu festival of lights, on Thursday amid concerns over the coronavirus pandemic and rising air pollution. Diwali is typically celebrated by socializing and exchanging gifts with family and friends. Many light oil lamps or candles to symbolize a victory of light over darkness, and fireworks are set off as part of the celebrations.

Last year, celebrations in India were upended by a renewed spike in COVID-19 infections, but festivities this year seem to be back. Even though the government has asked people to avoid large gatherings, markets have been buzzing ahead of Diwali, with eager crowds buying flowers, lanterns and candles. As dusk fell on Wednesday, over 900,000 earthen lamps were lit and kept burning for 45 minutes in the northern city of Ayodhya in Uttar Pradesh state, retaining the Guinness World Record it set last year. As part of the Diwali celebrations, the city last year lit 606,569 oil lamps.