Tag: infections

Categories
Health

Washington state infections and hospitalizations hit document

Washington state infections and hospitalizations hit record

An infection control nurse accompanies a patient who was born on Jan.

Karen Ducey | Getty Images

Covid-19 transmissions and hospitalizations in Washington state are at all-time highs, according to the state’s Department of Health.

On July 8, Washington recorded a Covid infection prevalence of 1 in 588 residents. Just one month later, on August 6, that number almost quadrupled to a Covid infection prevalence of 1 in 156 residents, the department said on Thursday. The latest numbers exceeded those of the state’s third wave of Covid infections in the winter of 2020.

According to a CNBC analysis of data from Johns Hopkins University, Washington state reports a seven-day average of 38.5 daily new cases per 100,000 population, ranking 22nd among all states.

Four counties had 14-day new infection rates of 500 per 100,000 Washington residents and five counties had rates of 300 to 500 per 100,000 residents. Sixteen counties had rates from 200 to 300 and 12 counties had rates from 100 to 200. The delta variant accounts for 98% of the cases in the state.

Hospital admissions in the state also rose, with a seven-day moving average of 29 hospital admissions for Covid on June 16. The number remained relatively low through July 8, but tripled by August 6 to a seven-day moving average of 96 hospital admissions for Covid symptoms. The state found that hospital admissions for people between the ages of 20 and 30 have increased, a trend seen in hospitals across the country as most older Americans were vaccinated.

Admissions to state hospitals for the unvaccinated and over 65s are six times higher than for those who are fully vaccinated. In people aged 16 to 64, unvaccinated people are ten times more likely to be hospitalized than their vaccinated counterparts. “If the entire population were to experience the hospitalization rates currently observed in unvaccinated people, the hospital system would be completely overwhelmed,” the state health department said in a statement.

Death rates have been down since Jan.

Immunity to prior infection in the state is only 15.5%, which would leave 84.5% of Washington residents unprotected if they did not have access to Covid-19 vaccines. According to the Ministry of Health, by August 16, 71.5% of the population aged 12 and over had received at least one dose of a Covid vaccine.

In the nationwide population, immunity to previous infections and vaccinations is 54.7%, an increase of only 2.8% since July 6.

“It is imperative to realize that literally any of us or our loved ones could be in need of hospital treatment in the near future,” said Acting State Science Director Dr. Scott Lindquist. “To ensure that care is available when needed, our hospitals are currently counting on each of us to be masked and vaccinated.”

CNBC’s Nate Rattner contributed to this report.

Categories
Health

Early information trace at an increase in breakthrough infections within the U.S.

Early data hint at a rise in breakthrough infections in the U.S.

Ever since Americans started rolling up their sleeves on coronavirus vaccines, health officials have said that people who are vaccinated are very unlikely to become infected or suffer from serious illness or death. However, preliminary data from seven states suggest that the arrival of the Delta variant in July may have changed the calculation.

Breakthrough infections in vaccinated individuals accounted for at least one in five newly diagnosed cases in six of these states and higher percentages of total hospital admissions and deaths than previously seen in any of them, according to figures compiled by the New York Times.

However, the absolute numbers remain very low and there is no doubt that the vaccines continue to provide effective protection. This is still “a pandemic of the unvaccinated”, as the federal health authorities have often said.

Still, the trend marks a change in how vaccinated Americans rate their risks.

“Remember when the early vaccine studies came out, it was like no one was hospitalized, no one died,” said Dr. Robert Wachter, chairman of the medical school at the University of California at San Francisco. “That is clearly not true.”

The numbers support the belief, widely held by Biden government officials, that some Americans could benefit from booster vaccinations in the coming months. Federal officials plan to approve additional shots as early as mid-September, though it’s not clear who will receive them.

“If the chances of a breakthrough infection have increased significantly, and I think the evidence is clear and the protection against serious illnesses is no longer as robust as it used to be, I think the case for boosters is rising quite a bit.” Fast, ” said Dr. Guardian.

The seven states – California, Colorado, Massachusetts, Oregon, Utah, Vermont, and Virginia – were examined because they have the most detailed data. It is not certain that the trends in these states apply to the entire United States.

In any case, scientists have always expected that the number of people who have been vaccinated will become more and more represented in the census of the seriously ill and the dead as the population grows.

“We don’t want to water down the message that the vaccine is hugely effective and protective, more than we initially hoped,” said Dr. Scott Dryden-Peterson, an infectious disease physician and epidemiologist at Brigham & Women’s Hospital in Boston.

“The fact that we are seeing groundbreaking cases and groundbreaking hospital admissions and deaths doesn’t detract from the fact that it still saves many people’s lives.”

The CDC declined to comment on the states’ numbers. The agency is expected to hold a press conference on Wednesday to discuss breakthrough infections, hospital admissions and vaccine effectiveness.

Most breakthrough infection analyzes have numbers collected through the end of June. Based on the cumulative numbers, the CDC and public health experts concluded that breakthrough infections are extremely rare and that vaccinated people are most unlikely to get seriously ill.

State data shows that vaccinated people are much less likely to get seriously ill or die of Covid-19.

Categories
Health

Breakthrough Infections and the Delta Variant: What to Know

What to Know About Breakthrough Infections and the Delta Variant

“Long Covid” is a poorly understood set of symptoms that can plague people for several months after an active infection has ended. While these symptoms eventually go away in many patients, “there is this subset of people who have long had Covid who just cannot recover,” said Akiko Iwasaki, an immunologist at Yale University.

Only a few small studies have looked at how common or how severely Covid can occur after breakthrough infections. It’s likely rare, say some experts, because breakthrough infections are unusual to begin with and of shorter duration.

In a study in Israel, about seven out of 36 people with breakthrough infections had symptoms that lasted more than six weeks. And in a survey of Covid-19 survivors, 24 out of 44 people with a symptomatic breakthrough infection reported persistent problems.

“We really need a broader national or even international survey,” said Dr. Iwasaki.

If you can survive a breakthrough infection relatively unscathed, you will likely get away with more robust protection against variants. Essentially, the infection acts as a booster shot, researchers say, boosting your immune system’s ability to recognize and fight the virus.

Studies have shown that when people recovering from Covid-19 receive even one dose of a vaccine, their antibody levels skyrocket. “I assume similar things would happen if you had a breakthrough infection,” said Dr. Iwasaki.

The vaccines train the immune system to recognize a piece of the original virus, a strategy that could leave us vulnerable to future variants. But any exposure expands the immunity repertoire, said Dr. Mina.

Eventually, through booster vaccinations or through repeated infections, our bodies will gain sufficient training in the virus to face versions with new mutations, he said, adding, “But we’re not there yet.”

Categories
Health

What to Know About Breakthrough Infections and the Delta Variant

What to Know About Breakthrough Infections and the Delta Variant

“Long Covid” is a poorly understood set of symptoms that can plague people for several months after an active infection has ended. While those symptoms eventually resolve in many patients, “there are this subset of people who have long Covid who just aren’t able to recover at all,” said Akiko Iwasaki, an immunologist at Yale University.

Only a couple of small studies have investigated how common or severe long Covid may be after breakthrough infections. It is likely to be rare, Dr. Iwasaki said, because breakthrough infections are uncommon to begin with and shorter in duration.

In one study in Israel, about seven of 36 people with breakthrough infections had persistent symptoms for more than six weeks. And in a survey of Covid-19 survivors, 24 of 44 people with a symptomatic breakthrough infection reported lingering problems.

“We really need a wider national or even international survey,” Dr. Iwasaki said.

If you get through a breakthrough infection relatively unscathed, you are likely to walk away with more robust protection against variants. The infection essentially acts as a booster shot, researchers say, strengthening your immune system’s ability to recognize and fight the virus.

Studies have shown that when people who recover from Covid-19 receive even one dose of a vaccine, their antibody levels skyrocket. “I expect similar things would happen when you have a breakthrough infection,” Dr. Iwasaki said.

The vaccines train the immune system to recognize a piece of the original virus, a strategy that may leave us vulnerable to future variants. But every exposure broadens the repertoire of immunity, Dr. Mina said.

Eventually, through booster shots or through repeated infections, our bodies will gain an education in the virus sufficient to counter versions with new mutations, he said, adding, “But we’re not there yet.”

Categories
Health

Covid delta will result in improve in breakthrough infections: Moderna

Covid delta will lead to increase in breakthrough infections: Moderna

The highly contagious Delta variant will lead to an increase in breakthrough infections in those who are fully vaccinated as people begin to exercise indoors after the summer, Moderna said Thursday.

While Moderna’s two-dose vaccine remains “stable” six months after the second vaccination, immunity to the coronavirus will continue to decline and ultimately reduce the vaccine’s effectiveness, the company said in the slides accompanying its second quarter earnings report were attached.

The company said its vaccine was 93% effective six months after the second dose. By comparison, Pfizer and BioNTech reported that their vaccine effectiveness decreased to about 84% after six months.

“Given this overlap, we believe a dose 3 refresh will likely be needed before the winter season,” wrote Moderna.

Moderna’s warning comes as the Delta variant becomes more widespread in more than 100 countries, including the United States. Delta, the predominant form of the disease in the United States, is more transmissible than the common cold, 1918 Spanish flu, smallpox, Ebola, MERS, and SARS, according to the Centers for Disease Control and Prevention.

A healthcare worker treats a patient in a negative pressure room in the Covid-19 Intensive Care Unit (ICU) at Freeman Hospital West in Joplin, Missouri, Tuesday, August 3, 2021.

Angus seed dressings | Bloomberg | Getty Images

For some Americans, concerns about the effectiveness of the vaccine have grown with the advent of the variant, which can cause more serious illnesses than the original coronavirus. Some people have even gone so far as to look for an extra dose not yet recommended by the CDC. This week, San Francisco health officials announced that they would allow patients who received the Johnson & Johnson vaccine to have a second vaccination from Pfizer-BioNTech or Moderna.

Drug makers have been saying for months that they expect people to need booster shots and perhaps additional doses annually at some point, just like they did with seasonal flu.

Moderna said Thursday that results from a Phase 2 study showed that a booster dose of its vaccine elicited a “robust” antibody response against three variants, including Delta.

The CDC and World Health Organization say booster doses are not currently required due to a lack of data. In fact, on Wednesday the WHO called on wealthy nations to stop distributing Covid booster vaccinations to give the world a chance to meet the WHO’s goal of vaccinating 10% of each country’s population by October.

“We need an urgent turnaround from moving the majority of vaccines to high-income countries and the majority to low-income countries,” said WHO Director-General Tedros Adhanom Ghebreyesus.

The move comes after Israel announced that the country will be giving booster doses to its elderly population. The Dominican Republic has also given its population booster doses, while neighboring Haiti recently secured its first vaccine doses.

People in the US are also finding ways to get booster vaccinations.

– CNBC’s Rich Mendez contributed to this report.

Categories
World News

Delta Variant, R.S.V. Infections Rising Amongst Kids

Delta Variant, R.S.V. Infections Rising Among Children

Health officials have raised concerns about a simultaneous rise in Delta infections and cases of Respiratory Syncytial Virus (RSV), a highly contagious, seasonal flu-like illness that is more likely to affect children and older adults.

Cases of RSV have risen gradually since early June, with an even bigger increase over the past month, according to data from the Centers for Disease Control and Prevention. RSV, which can cause symptoms such as a runny nose, cough, sneeze, and fever, usually begins to spread in the fall, which makes this summer unusual.

In a series of posts on Twitter, Dr. Heather Haq, a pediatrician at Texas Children’s Hospital in Houston, reported a surge in hospital admissions from coronavirus and RSV.

“After many months with no or few pediatric Covid cases, we are seeing infants, children and adolescents with Covid flow back to the hospital more and more every day,” she wrote, adding that the ages of the patients ranged from 2 weeks to 17 Years old, including some with Covid pneumonia.

“We are at the front end of a huge surge in Covid,” wrote Dr. Haq, who was unavailable for comment on Sunday. “We now have winter-level patient numbers of acutely ill infants / toddlers with RSV, and I fear we will run out of beds and staff to handle the surge.”

Coronavirus Pandemic and Life Expectancy in the United States

RSV cases in Texas began to increase in early June and appeared to peak in mid-July, according to the state Department of Health.

There has been a similar surge in RSV cases in Florida, where infections “were higher than in previous years at this point in time,” according to a surveillance report.

In Louisiana, where cases have risen 244 percent in the past two weeks, Our Lady of the Lake Children’s Hospital in Baton Rouge was nearing capacity on Friday, CNN reported.

“You start with the pandemic for the last 18 months and then with RSV for the last few months. It just seems like one thing at a time that keeps our teams very busy, ”said Dr. Trey Dunbar, president of the hospital, the network.

In Oklahoma, where RSV cases have also risen sharply, hospital beds are becoming scarce.

“We’re just asking everyone to do their best to help a tense hospital situation,” an Oklahoma children’s hospital said in a Facebook post last week.

Dr. Cameron Mantor, the chief medical officer of Oklahoma Children’s Hospital at OU Health, told The Oklahoman that RSV cases in the state have remained “exponentially off the charts” in the past two months.

“RSV is a real problem right now,” he told the newspaper. “What will happen when we have an increase in pediatric Covid cases?”

The surge in RSV cases is due to the fact that new coronavirus infections in the United States rose 148 percent in the past two weeks and hospital admissions rose 73 percent, according to the New York Times.

The rise in coronavirus infections has been largely attributed to the highly contagious Delta variant and, in some states, to low vaccination rates.

“I am concerned if the children go back to school with the circulating delta we will see huge school breakouts that we have not seen in previous waves and disproportionately affect the children,” wrote Dr. Haq. “I’ve looked after hospital patients with Covid throughout the pandemic, but this time we’ll see more pediatric Covid shots with unvaccinated, susceptible children plus Delta variant.”

Texas Governor Greg Abbott has banned local governments and state agencies from prescribing vaccines and preventing local officials from requesting face masks.

Florida could face similar virus challenges early in the school year. Governor Ron DeSantis has spoken out against new masking recommendations from the CDC, and his office said in a statement last week that “parents know what is best for their children”.

Excess RSV infections have also been reported from places like New Zealand, which is currently winter. Experts there say children may be more susceptible than usual to seasonal viruses and infections because they were exposed to germs during lockdown at the beginning of the pandemic.

Categories
Health

Why Vaccinated Folks Are Getting ‘Breakthrough’ Infections

Why Vaccinated People Are Getting ‘Breakthrough’ Infections

Whether a vaccinated person ever becomes infected may depend on how high antibodies spiked after vaccination, how potent those antibodies are against the variant, and whether the level of antibodies in the person’s blood has waned since immunization.

In any case, immune defenses primed by the vaccines should recognize the virus soon after infection and destroy it before significant damage occurs.

“That is what explains why people do get infected and why people don’t get seriously ill,” said Michel C. Nussenzweig, an immunologist at Rockefeller University in New York. “It’s nearly unavoidable, unless you’re going to give people very frequent boosters.”

Today’s Best Reader Comments

Understand the State of Vaccine Mandates in the U.S.

There is limited evidence beyond anecdotal reports to indicate whether breakthrough infections with the Delta variant are more common or more likely to fan out to other people. The C.D.C. has recorded about 5,500 hospitalizations and deaths in vaccinated people, but it is not tracking milder breakthrough infections.

Additional data is emerging from the Covid-19 Sports and Society Workgroup, a coalition of professional sports leagues that is working closely with the C.D.C. Sports teams in the group are testing more than 10,000 people at least daily and sequencing all infections, according to Dr. Robby Sikka, a physician who worked with the N.B.A.’s Minnesota Timberwolves.

Breakthrough infections in the leagues seem to be more common with the Delta variant than with Alpha, the variant first identified in Britain, he said. As would be predicted, the vaccines cut down the severity and duration of illness significantly, with players returning less than two weeks after becoming infected, compared with nearly three weeks earlier in the pandemic.

But while they are infected, the players carry very high amounts of virus for seven to 10 days, compared with two or three days in those infected with Alpha, Dr. Sikka said. Infected players are required to quarantine, so the project has not been able to track whether they spread the virus to others — but it’s likely that they would, he added.

Categories
Health

Music competition within the Netherlands results in over 1,000 Covid infections

Music festival in the Netherlands leads to over 1,000 Covid infections

Members of the public walk at Vondelpark in Amsterdam on a sunny day on March 30, 2021.

EVERT ELZINGA | AFP | Getty Images

A festival in the Netherlands shocked officials after 1,000 coronavirus infections were linked to the event despite requiring an “entry test”.

The Verknipt outdoor festival, which took place in Utrecht at the beginning of July, was attended by 20,000 people over two days. Each participant had to show a QR code stating that they had been vaccinated, had recently had a Covid infection or had a negative Covid test.

The organizers insisted that the event was carefully planned and controlled, but despite this, 1,050 people who attended the festival have since tested positive for Covid, according to the Utrecht Regional Health Authority.

“We can’t say that all these people infected themselves at the festival, it could also be that they got infected on the trip to the festival or the evening before the festival or an after party. re (the cases) are all connected to the festival, but we cannot 100% say that they were infected at the festival, “said Lennart van Trigt, a spokesman for the Utrecht Health Department (GGD).

Nonetheless, he said the number of cases was “pretty staggering” and could increase slightly in the coming days.

The event highlighted problems with the “entry test,” added van Trigt, which allowed people to take Covid tests up to 40 hours before the event, which opened up the possibility of contracting Covid in the meantime.

“We have now found out that this deadline is too long. We should have had 24 hours [period], that would be much better because in 40 hours people can do a lot of things like visit friends and go to bars and clubs. So in a 24-hour period, people can do fewer things and it’s safer, “he said.

Another problem was that people in the Netherlands could get a Covid pass for the festival immediately after vaccination, while in reality it takes several weeks for immunity to build up after a Covid vaccination.

“We were a little too happy with the trigger,” said Van Trigt, noting that there were lessons to be learned from.

The mayor of Utrecht, Sharon Dijksma, was particularly condemned while attending the ill-fated festival.

The Netherlands has seen a staggering increase in Covid cases in recent weeks, especially after lifting bar and club restrictions in late June and subsequently increasing Covid among younger people.

Dutch Prime Minister Mark Rutte and his Health Minister Hugo de Jonge apologized on Monday, saying the government made a “misjudgment” of lifting restrictions too early.

De Jonge also apologized for his “Dansen met Janssen” (“Dancing with Janssen”) campaign, which promoted the unique Janssen Covid vaccine to young people so that they could go out to party.

After the government admitted that “the coronavirus infection rate in the Netherlands has increased much faster than expected since the society was almost completely reopened on June 26,” the government announced last Friday that nightclubs and live performances would be at least until August 13th to be closed again.

The country’s “R” number is now 2.17, meaning any person with Covid-19 is likely to infect at least two other people.

An additional 10,492 cases were reported in the country on Wednesday, more than the average number of daily cases (8,395) over the past seven days. The majority of new cases affect people between the ages of 20 and 29 years.

Categories
Health

This is a map displaying the place low vaccination charges meet excessive case counts as infections surge

Here's a map showing where low vaccination rates meet high case counts as infections surge

In more and more US states with low vaccination rates, Covid cases are rising, exposing residents to the risk of “unnecessary” infections, hospitalizations and possibly death as the Delta variant rips across the country, according to US health officials.

“After several weeks of falling case numbers followed by a long plateau, we are now seeing an increase in the number of cases in many parts of the country,” said Dr. Jay Butler, CDC assistant director, infectious diseases, on a call hosted Tuesday by an industry group. Hospitalization rates, which tend to lag behind confirmed cases, are similarly starting to rise, he said.

A CNBC analysis of US vaccination rates and Covid cases shows that there are 463 counties in the United States with high rates of infection – which have reported at least 100 new cases per 100,000 residents in the last week – more than double the US rate . The majority of these counties, 80%, vaccinated less than 40% of their 23 million residents, analysis shows data from the Centers for Disease Control and Prevention and Johns Hopkins University.

More than half of the counties in Missouri, Arkansas and Louisiana have low vaccination rates and increased Covid cases, according to CNBC analysis. These three states had some of the highest cases per capita in the country in the past seven days as the spread of the Delta variant increased in southwest Missouri.

“There will continue to be an increase in cases among unvaccinated Americans and in communities with low vaccination rates, especially given the spread of the more transmissible Delta variant,” Jeff Zients, White House Coronavirus Response Coordinator, told a news conference last week . Virtually all Covid hospital admissions and deaths, 99.5%, occur in those who have not been vaccinated, US officials say.

In fact, nationwide cases are on the rise again as the highly transmissible delta variant asserts itself as the dominant strain in the US. The seven-day average of newly confirmed Covid cases has risen to about 23,300 per day, almost double the weekly average, according to data from Johns Hopkins before.

The rise of the Delta variant has spurred officials in some states like Mississippi to issue new calls for masking and social distancing, especially among older and more vulnerable residents.

“When the Delta strain emerged (in Utah) it quickly became the dominant strain, and by dominant I don’t mean 50%. For the last full week of data, more than 80% of the sequence viruses were Delta viruses and so far this week are it is 92% of all variants, “said Dr. Andrew T. Pavia, director of the Department of Pediatric Infectious Diseases at the University of Utah School of Medicine, in a call hosted Tuesday by the Infectious Diseases Society of America.

“If you think about what it means to have such a rapid virus takeover, it means that it is the most suitable virus, that it spreads more efficiently, that it spreads in unvaccinated pockets, and many diseases cause a lot of stress inside” , he added.

Mississippi has given at least one injection to just 37% of its population, making it last in the country. Officials there urged people over 65 and immunocompromised residents to avoid indoor mass gatherings in the next two weeks in the event of “significant transmission” of the Delta variant in the coming weeks.

“We don’t want anyone to die unnecessarily,” said Dr. Mississippi State Health Commissioner Thomas Dobbs during a news conference Friday.

According to Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, as successful in preventing serious illness, hospitalizations and deaths from the Delta variant.

Breakthrough infections are rare, and around 75% of people who die or are hospitalized after being vaccinated with Covid are over 65 years old, according to the CDC.

“Preliminary data for the past six months suggests that 99.5% of deaths from Covid-19 in the states have occurred in unvaccinated people … the suffering and loss we see now are almost entirely preventable,” Walensky said Earlier this month.

In addition to the risk of disease for Americans who have not yet received a vaccination, unvaccinated sections of the population could threaten the country’s ability to control the pandemic. Continued transmission of the virus means additional opportunities for new variants to emerge with the ability to bypass vaccine protection.

While 48% of Americans are fully vaccinated, the pace of daily vaccinations has slowed significantly in recent months. According to CDC data, an average of about 515,000 vaccinations were administered daily for the past week, after a steady decline from the peak of more than 3 million daily vaccinations.

President Joe Biden renewed his administration’s efforts to increase vaccination rates after failing to meet his July 4th goals, with a focus on youth and increasing availability in places like doctor’s offices and work environments.

Nearly 1,600 counties in 40 states with 72 million people have vaccinated less than 40% of their population, according to CNBC analysis. Six states where vaccination data were not available at the county level were excluded from the analysis.

Categories
Health

Most absolutely vaccinated individuals who get Covid delta infections are asymptomatic, WHO says

Most fully vaccinated people who get Covid delta infections are asymptomatic, WHO says

World Health Organization Director General Tedros Adhanom Ghebreyesus R speaks at a daily briefing in Geneva, Switzerland.

Chen Junxia | Xinhua News Agency | Getty Images

People fully vaccinated against Covid-19 still get the Delta variant, but global health officials said the vaccinations saved most people from getting seriously ill or dying.

“There are reports that vaccinated populations have cases of infection, particularly with the Delta variant,” said Dr. Soumya Swaminathan, the chief scientist of the World Health Organization, at a press conference on Monday. “Most of these are mild or asymptomatic infections.”

However, hospital admissions are on the rise in some parts of the world, especially where vaccination rates are low and the highly contagious Delta variant is spreading, she said.

In the US, officials said virtually all recent hospital admissions and deaths from Covid have occurred in people who have not been vaccinated. Breakthrough infections are rare, and about 75% of people who die or are hospitalized after being vaccinated with Covid are over 65, according to the Centers for Disease Control and Prevention.

“The Delta variant is spreading around the world at a breakneck pace, driving the number of cases and deaths again. However, the same hit does not suffer everywhere,” said WHO Director General Tedros Adhanom Ghebreyesus. “We are in the midst of a growing two-pronged pandemic, with the haves and the have-nots growing divergent within and between countries in high-vaccination locations.”

The variant spreads quickly and infects unprotected and vulnerable people, he said.

Swaminathan warned that vaccinated people can still get Covid and pass it on to others, which is why WHO officials have urged people to continue wearing masks and practice social distancing. “But it certainly greatly reduces your chances of severe hospitalization and death,” she added.

Some studies have shown that those who are infected with Covid after vaccination produce much fewer virus than those who are not vaccinated, which reduces the risk of spreading the virus to others. WHO officials said more studies are needed to understand the impact of the vaccines on transmissibility.