A study published today in the Journal of the American Medical Association suggests that vaccinating kids against H1N1 helps protect their entire community.

The researchers set out to test the idea of herd immunity and the observation that “[c]hildren and adolescents appear to play an important role in the transmission of influenza.”

The randomized, blinded study examined 46 volunteer Canadian Hutterite colonies. Roughly 80% of children aged 3 to 15 in half the colonies were given an H1N1 vaccine. Roughly 80% of those in the other colonies were given a hepatitis A vaccine.

Comparing the two populations, the study determined that vaccinating children against H1N1 “conferred 61% indirect protection against influenza among persons who did not receive the study vaccine.” The overall conclusion:

Our data suggest that a significant herd immunity effect can be achieved when the uptake of vaccine is approximately 80% in clusters in which children and adolescents aged 3 to 15 years are immunized.

The authors also propose that elderly people may benefit more from child-based herd-immunity than from being vaccinated themselves:

Although there were relatively few elderly individuals in this population, the protective effect is likely comparable with or greater than what can be achieved by direct immunization.

Helen Branswell, medical reporter for The Canadian Press, notes that children may not necessarily be the key to herd immunity:

Dr. Allison McGeer, an influenza expert at Toronto’s Mount Sinai Hospital, questioned whether the effect was due to the fact that Loeb’s team vaccinated kids, or just to the fact that they vaccinated a sizable portion of the population of the colonies randomized to get flu shots.

The New York Times piece about the study is here. The National Institute of Allergy and Infectious Diseases press release is here.

Two different assessments of U.S. immunity to H1N1 have emerged recently. The first suggests the number of Americans infected by swine flu in 2009 (roughly 63 million). The second estimates the number of Americans who currently have immunity to H1N1 (somewhere roughly between 150 and 165 million).

Ted Ross [U. of Pittsburgh]

Assessment #1: A new study published in PLoS Currents: Influenza estimates the number of Americans who were infected with H1N1 in 2009. (Read our post about PLoS — the Public Library of Science — here.) The lead author is Ted Ross, an associate professor of microbiology and molecular genetics at the University of Pittsburgh.

The study looks at levels of antibodies to 2009 H1N1 in Pittsburgh-area residents. (Infection with a virus stimulates antibody production, which then confers immunity.) It examines blood from “846 persons that ranged in age from 1 month to 90 years of age.” The samples were taken from “hospital and clinic patients in mid-November and early December 2009.”

It’s possible that some people with antibodies to 2009 H1N1 got them from the vaccine rather than infection with the virus — but “the timing of the sampling relative to vaccine availability in Pittsburgh suggests that these samples are likely from a largely unvaccinated population during the peak of the second pandemic wave.” In other words: the data probably approximate the number of people actually infected by H1N1 in 2009.

Here’s the study conclusion in a nutshell:

21% of persons in the Pittsburgh area had become infected and developed immunity. Extrapolating to the entire US population, we estimate that at least 63 million persons became infected in 2009. As was observed among clinical cases, this sero-epidemiological study revealed highest infection rates among school-age children.

Ian York [Michigan State University]

Assessment #2: Ian York, an assistant professor of microbiology and molecular genetics at Michigan State University, recently offered his best educated guess of the number of Americans now immune to H1N1 (on his blog Mystery Rays from Outer Space). As he puts it, there are three ways in which someone could have acquired immunity:

They could have been exposed to a related virus, some time in the past, and have developed a long-term immunity. They could have been infected with [H1N1], somewhere in the first or second wave. Or, of course, they could have been vaccinated.

He collects the available data for each of those categories — emphasizing that “[t]hey’re more or less approximate” — and concludes that:

• Over half the US population as a whole is now immune to the new [H1N1].
• As many as three-quarters of the elderly and two-thirds of the children — the most important populations as far as flu is concerned — may be immune.
• Between a third and about half of this immunity was due to vaccination.

To find York’s full table of high and low estimates — broken down by age group — click here.

Why is it useful to know what percentage of the population may have immunity to H1N1? As the PLoS study puts it, it “provides valuable information about the likelihood of a possible third wave and may be useful in decision-making about immunization strategies.” Or as York writes, the “level of immunity” that he calculated “is probably enough to impact virus transmission drastically.”

Today WHO recommended that next winter’s seasonal-flu vaccine include H1N1. Keiji Fukuda, WHO’s resident pandemic-flu expert, apparently cautioned in a press conference, however, that “[t]he inclusion of the H1N1 pandemic virus in the influenza vaccine does not signal that the pandemic is over.” WHO will meet next week to determine whether the pandemic is waning.

Here are the three viruses WHO recommended for the 2010/11 vaccine:

– an A/California/7/2009 (H1N1)-like virus;
– an A/Perth/16/2009 (H3N2)-like virus;*
– a B/Brisbane/60/2008-like virus.

* A/Wisconsin/15/2009 is an A/Perth/16/2009 (H3N2)-like virus and is a 2010 southern hemisphere vaccine virus.

Click here for a link to a PDF of the full report.

Yesterday, at the 2010 Public Health Preparedness Summit, Health and Human Services Secretary Kathleen Sebelius assessed the federal response to H1N1. (The summit was spearheaded by National Association of County and City Health Officials.)

Sebelius’s overall tone was positive. She felt the government’s preparation for “all hazards” allowed it to “hit the ground running.”

One of the first steps we took after identifying the flu was to release 11 million antiviral doses, 13.5 million surgical masks, and more than 25 million respirators from our Strategic National Stockpile. Having these countermeasures on hand allowed us to ensure that commercial shortages didn’t slow our response.

She also cited the effectiveness of the Hospital Preparedness Program, which she said guided hospitals “when their emergency rooms and ICU beds started filling up.”

Sebelius highlighted, too, HHS’s “unprecedented multimedia communications campaign,” which “taught an entire generation of kids how to sneeze” and rebuilt flu.gov.

Sebelius pointed to “partnership with state, local, tribal and territorial public health officials” as another critical pillar of the federal response.

But what were the lessons learned? HHS, Sebelius said, is currently conducting a full review. One of the obvious lessons that has already emerged: partnerships outside the public-health community are vital (e.g., with schools, which provided vaccine clinics for many children).

The other standout lesson is that vaccine production needs to be improved. Sebelius praised the speed with which vaccine development began but conceded that “outdated” manufacturing processes caused frustrating delays. As she put it, “there was nothing we could do to make the vaccine grow faster in eggs.” The US needs to make “long-term investments,” she said, in “faster and more reliabl[e]” vaccine technology.

Finally, Sebelius recognized the fragility of the budget-strapped state and local public-health infrastructure.

Ultimately, Sebelius said, HHS needs to aim for this:

[A] modernized countermeasure production process where we have more promising discoveries, more advanced development, more robust manufacturing, better stockpiling, and more advanced distribution practices.

Some local public-health officials — like those in Seattle and King County in Washington — are starting assessments of their own. And some appear less upbeat than Sebelius. The chief of communicable-disease control for King County, for example, feels “‘we need to be much more prepared. [...] This should be a wake-up call.’”

How are your state and local public-health departments evaluating their H1N1 response? And do residents and health-care workers in your town or state see the same successes and failures?

The World Health Organization has been accused recently, largely in Europe, of hyping the danger of H1N1 as a result of pressure from the pharmaceutical industry.

WHO has fired back.

In a statement released a few days ago, it explains that its work necessitates “global cooperation with a range of partners, including the private sector,” but that it “guard[s] against the influence of any improper interests”:

Numerous safeguards are in place to manage conflicts of interest or perceived conflicts of interest among members of WHO advisory groups and expert committees. Expert advisers provide a signed declaration of interests to WHO detailing any professional or financial interest that could affect the impartiality of their advice.

(More details on the safeguards here.)

WHO’s Dr. Keiji Fukuda defended the Organization this week in front of the Council of Europe. He explained that WHO’s “influenza pandemic preparedness plan,” which “provide[s] recommended actions to be taken by countries and WHO depending on the real world situation” — a public document — was “based upon the collective input of public health and scientific experts from around the world.”

He also stressed that International Health Regulations assure an “orderly, rules-based framework for detecting, assessing, reporting, declaring and responding to public health emergencies,” and that they offer “a system of checks and balances to ensure that no one, including the WHO Director-General, has unfettered power when making decisions.”

Finally, Fukuda emphasized that H1N1 unquestionably meets the definition of a pandemic:

This current influenza pandemic is a scientifically well-documented event in which the emergence and spread of a new influenza virus has caused an unusual epidemiological pattern of disease throughout the world. This is not an arbitrary matter of word-smithing, definitions or polemics. The labelling of the pandemic as “fake” is to ignore recent history and science and to trivialize the deaths of over 14,000 people and the many additional serious illnesses experienced by others.

WHO enumerates elements of this “scientifically well-documented event”:

Lab analyses showed that this influenza virus was genetically and antigenically very different from other influenza viruses circulating among people

Epidemiological information provided by Mexico, the US and Canada demonstrated person-to-person transmission.

Clinical information, especially from Mexico, indicated this virus also could cause severe disease and death. At the time, those reports did not indicate a pandemic situation, but taken together sent a very strong warning to WHO and other public health authorities to be ready for one.

As the pandemic evolved, clinicians identified a very severe form of primary viral pneumonia, which was rapidly progressive and frequently fatal, that is not part of the disease pattern seen during seasonal influenza. While these cases were relatively rare, they imposed a heavy burden on intensive care units.

Geographical spread was exceptionally rapid.

WHO has also pointed out that it “has consistently assessed the impact of the current influenza pandemic as moderate.”

Children’s Hospital Boston and Health and Human Services have developed together a Facebook application called “I’m a Flu Fighter!”

The app is part of a project designed “to empower individuals to promote positive health behaviors amongst their friends and family through the use of social networks.”

It has several elements: you can pick a flu-fighter character for your profile, advertise your vaccination status, and “challenge” your FB friends to “join you in the fight against flu.” It also includes info on flu vaccines.

Here’s the short course: The vaccine is now available to pretty much everyone who wants it all across the country. So far, the US hasn’t decided to return/donate/sell any of its vaccine supply as some European countries are doing. Instead, it’s focusing on the upcoming (10-16 January) National Influenza Vaccine Week (NIVW). NIVW is another big push to encourage Americans to get H1N1 and seasonal-flu shots. It has its own schedule of activities, informational materials, a media toolkit, and web tools like ecards and badges.

Why continue pushing the H1N1 vaccine when, as Schuchat announced, “we’re seeing drops in laboratory confirmed hospitalizations and deaths”? Because there’s also “activity increasing in a few other indicators.” She clarified:

We still have more activity than we usually have this time of year, though it’s certainly much below where it was several weeks ago. All the virus that we’re seeing right now is the H1N1 virus. We haven’t yet seen the emergence of seasonal flu strains in any numbers at all. We saw a slight uptick in the last week’s reporting in the influenza-like illness visits to the doctors or emergency departments. That can sometimes happen right around Christmas, so we don’t know if that will persist. We also saw an uptick in pneumonia or influenza deaths in this past week. And that isn’t something that we necessarily see around the Christmas holiday.

Minnesota was one state that reported increased influenza-like illness last week.

What CDC is afraid of, of course, is a third wave of H1N1. To drive the point home, Schuchat showed this graph of pandemic mortality in 1957:

[CDC / usable on your site]

She went on to say:

This is really a reminder of why we are saying that we need to remain vigilant. [...] [I]f you look at this graph, the bottom part of that curve, you know, the — there’s the camel hump and then it comes down to that valley. Well, that’s where we are right now in that valley. We don’t know what’s going to happen over the next several weeks or months. But in 1957, this essentially gave the all clear whistle in that December/January time period. They had vaccine, but they didn’t encourage its use and yet they did go on to see that increase in mortality.

National Influenza Vaccine Week launches on Sunday. You can check here for NIVW activities in your area.

[HHS]

While the US government continues to push the vaccine actively, the recent news from Canada and a number of European countries is the surplus vaccine supply. Even some developing countries slated to receive donated vaccine from WHO appear to be reassessing the quantity they need.

Two polls released just before the holidays give some new figures on H1N1 vaccination rates in the US: one by the Harvard School of Public Health (HSPH) and one by the National H1N1 Flu Survey (NHFS). The HSPH poll was conducted on 16-17 December, 2009. The NHFS poll was conducted on 6-12 December, 2009.

The HSPH results include the following:

The NHFS results include these numbers:

A new article in Biotechnology Journal proposes a method of producing influenza vaccine that’s more efficient than the traditional egg-based technology. It uses “virus-like particles” (VLPs) created in insect cells to form the basis of a vaccine. (This technology is apparently already approved for vaccines against some other diseases.)

The article was written by scientists in Austria who produced a VLP vaccine against H1N1 that, in mice at least, triggered a robust immune response. If this type of vaccine becomes a viable option for humans, its production speed would help public-health authorities respond more quickly to flu pandemics and viral mutations.

Veteran flu journalist Maryn McKenna cautioned recently, however, that emerging vaccine technologies like this one “remain in the realm of basic science or in preclinical testing” for influenza. In other words: flu-vaccine production will probably still rely on chicken eggs in the immediate future.