Updated October 27, 2009.
I am a family practice physician who wishes to write a balanced presentation of facts - no fear mongering in either direction. In the article below I often use the misnomer "swine flu" since it is by this name that the general public has come to know this virus. I am not trying to be "politically correct" here - scientifically the virus has swine, avian, and human influenza virus components - it's just too cumbersome and wordy to write "2009 pandemic H1N1 influenza A" when "swine flu" is understood. "Seasonal flu" refers to the strains of influenza we see in "non-pandemic" years.
Disclosure: I have no ties, financial or otherwise, to the government or pharmaceutical companies. I do own mutual funds which invest in thousands of different companies. I do not benefit financially if patients are vaccinated (reimbursement covers just the cost of vaccine, and there is no mark-up).
The virus which started this pandemic was first identified in Mexico in March 2009, and then in California in April 2009. Influenza vaccine takes 5-8 months to invent, test, produce, test again, manufacture on a large scale, allocate, distribute, and administer. The chicken egg-based process has its limitations. A case could be made to develop other methods to improve speed and allow people allergic to egg proteins safe access to vaccine.
Clinical trials of several thousand people show that the swine flu vaccine is safe, but it is reasonable to expect rare serious reactions to occur once millions of people are vaccinated. More commonly, some people feel arm soreness or generalized malaise for a few days after the shot. This is a reaction of the body's immune system to the vaccine. You cannot get the actual influenza infection from either swine or seasonal flu shots. The vaccine will likely save tens of thousands of lives, some of them through herd immunity if a critical percent of people in communities get vaccinated. The absolute benefit of the vaccine will obviously be reduced by any delays there are in getting vaccinated.
Unvaccinated, the estimated case fatality rate for swine flu is similar (we won't know more precise numbers for a few months) to the seasonal flu, "only" 0.01-0.1%. This is lower than in 1918, and comparable to 1957 & 1968. We can expect more people to get the influenza this season than in normal flu seasons since this is a pandemic - there is little natural immunity to this new virus in the general population. If 100 million (one third of the U.S. population) people get infected, this means approximately (ballpark figure; it won't be 1,000 or 1 million) 10,000-100,000 deaths. The practical benefit for most people isn't preventing hospitalization or death, but rather it's like an "insurance policy" against getting influenza and missing a week of work or staying home to care for a sick child, or for that college student who doesn't want to risk getting sick during final exams week in the heart of flu season.
The injectable swine flu vaccine was 97% effective in adults in triggering a protective antibody level in a clinical trial, 93% in the elderly. In real life, don't count on numbers this good, maybe 90%. The data from another study in children show that those 11 and younger require 2 shots to achieve protective levels of antibody. The seasonal flu vaccine is only 60-80% effective and even lower for elderly (as low as 30%). Herd immunity is very important for seasonal flu. Elderly seem to have some natural immunity to swine flu, and this may be due to the fact that variations of the 1918 H1N1 were in wide circulation until the 1957 pandemic of H2N2. Seasonal H1N1 disappeared until 1977, and ironically, may have reappeared due to accidental lab release. Surprisingly and dishearteningly, young and healthy people and pregnant women seem to be dying from swine flu, which is different from seasonal flu which mostly just kills elderly, immunocompromised (i.e. weakened immune systems), the very young, and those with serious underlying medical conditions (notably heart, lung, and dialysis patients).
A nice source of the latest statistics on the extent of pandemic influenza is http://www.cdc.gov/flu/weekly/ - note the time lag between the dates data are available for and the current date.
There is a Japanese study showing influenza vaccine saves lives. I include this because it demonstrates what happened when the shot was mandatory for school children, and then deaths increased after the shot was made optional. Also, there are no U.S. politics, drug companies, or conspiracies involved. http://content.nejm.org/cgi/content/full/344/12/889
Hygiene is the best way to avoid getting influenza (seasonal or swine). I'd suggest using a paper towel to touch faucets and doors in public places and avoiding shaking hands (just tell a white lie that you're coming down with something, and this awkward impolite moment turns into a "thank you for being concerned about my health" moment). Grocery carts and groceries others (i.e. other customers, stockers, and the cashier) have touched are also sources of infection. Also, avoid touching your eyes/nose/mouth with unwashed hands. Cough and sneeze into your elbow. Disinfectant wipes are convenient and effective in situations where hand washing is impractical. Antimicrobial soap is not necessary.
Patients who decide to get the swine and / or seasonal flu shots should be aware that currently about 99% of flu cases are swine flu (a type of influenza A abbreviated as S-OIV H1N1 = swine-origin influenza virus H1N1). As we move into winter, we might see more seasonal flu strains (a different H1N1 influenza A, H3N2 influenza A, and influenza B). But, as per past pandemics, the new strain tends to dominate and replace the old strains in circulation in the community. Therefore, we could very well see that most cases this fall / winter are swine flu, and thus the swine flu vaccine might be more important to get than the regular seasonal influenza vaccine.
A study reported to me on 10/7/09 via email said that the seasonal flu vaccine might give partial protection against swine flu. An unpublished report from Canada shows the opposite effect - that one vaccine weakens the benefit of the other vaccine by half. In light of this uncertainty, some infectious disease specialists have recommended a 2 week delay between the vaccines. Practically speaking, this phenomenon will have already occurred in many situations due to the delays in receiving the swine flu vaccine from its foreign manufacturers.
The facts on the 1976 "swine flu" vaccine debacle (i.e. there was no pandemic, false alarm, different from 2009): 532 people got Guillain-Barre out of 40 million vaccinations, and of those, 32 people died. http://content.nejm.org/cgi/content/full/361/3/279. This year's swine flu is very different from the strain in 1976. Since then, flu vaccines are associated with (not necessarily cause and effect) a 1 in 100,000 to 1,000,000 chance of getting Guillain-Barre. This is smaller than the chance of death from swine flu.
Most swine flu shots, and seasonal flu shots from multi-dose vials, have 25 micrograms (0.025 milligrams) of mercury in the form of thimerosal (contains ethyl mercury) as a preservative. The half life of ethyl mercury is 7 - 10 days, so it is out of your system within a few weeks (4 half lives). I believe it is safe according to research studies. Opponents of my view cannot cite any clinical study showing it to be unsafe. Here is one study showing that it is safe: http://content.nejm.org/cgi/content/full/357/13/1281. Due to public outcry, thimerosal has not been present in routine childhood vaccines since 2001 (some non-routine childhood shots do have thimerosal). The quantity of mercury is comparable to what we get from our environment (doesn't necessarily make it O.K.) or food (e.g. a can of tuna).
The nasal swine flu vaccine has no mercury, but only a limited number of doses will be available. It is indicated in non-pregnant healthy people age 2-49. I am unaware of any reports of serious adverse reactions with the seasonal version of this vaccine in prior years or the new pandemic H1N1 nasal vaccine. There are some restrictions because it is a live-attenuated virus. http://www.cdc.gov/flu/about/qa/nasalspray.htm. Another downside is it may not be as effective as the injectable vaccine, since the seasonal version of the nasal vaccine was less effective than the injectable version in this study: http://content.nejm.org/cgi/content/full/361/13/1260.
Some anti-vaccine people are propagandizing the fact that the State of Washington suspended its strict law on legal limits for mercury content of vaccines. The 0.5 microgram limit was the equivalent of banning all vaccines with thimerosal. Some seasonal flu and most swine flu vaccines have 25 micrograms of mercury, thus lifting the ban was the equivalent of making those shots legal in Washington (they are legal in the other 49 states). Instead of being part of a "government conspiracy," the State of Washington was actually getting in line with all the other 49 states, putting the decision whether or not to get the vaccine back in the hands of patients and their physicians. http://www.doh.wa.gov/cfh/Immunize/documents/parentinfo5305.pdf and http://www.vaccinesafety.edu/thi-table.htm.
I realize there are certain people that won't believe medical facts because they don't trust the government, pharmaceutical companies, CDC, WHO, doctors, the health system in general, etc. The current health care reform debate is fueling a lot of the rhetoric. The virus could care less about one's personal politics. It's a free country. Shots are not mandatory. And even if you get influenza you've got a 99.9-99.99+% chance of coming out fine.
The swine flu will rarely kill humans, and the vaccine will have even fewer serious adverse reactions - for those few individuals, the flu season will be tragic. A non-medical analogy to this debate is playing the lottery - you cannot expect to win, but the investment is minimal when purchasing one ticket. Patients should make informed decisions about their health care based on unbiased facts, and I have tried my best to present what I feel to be relevant. Patients also should consult with their personal physicians to discuss their concerns. Regardless, I think we all should hope that the flu season is not too severe, and that the vaccine causes minimal problems.