Ramifications of adverse events in children in Australia
BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c2994 (Published 09 June 2010) Cite this as: BMJ 2010;340:c2994
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Peter Collignon and his colleagues do not exaggerate the problem of
adverse
event underreporting. VAERS (Vaccine Adverse Events Reporting System) is
the voluntary system used in the U.S. to signal vaccine side effects.
During
the 18-year period from 1990 through 2007 just 88 cases of Kawasaki
Disease in children under 5 were reported to VAERS. During the same
period
about 88 million U.S. children passed through the 0-5 age group;
consequently the incidence rate reported to VAERS was 0.10 KD cases per
100,000 person-years. (Pediatr Infect Dis J 28:943, 2009) From 1988 to
2006 the published KD incidence for U.S. children under 5 rose from 11.0
to
20.8 per 100,000 person-years. (Pediatrics 111:448, 2003. Pediatrics
112:495, 2003. Pediatr Infect Dis J 29:483, 2010) Even for infants 3-6
months old, when suspicion for vaccine adverse effects should be
especially
high, KD incidence as reported to VAERS was 0.11 while published
background rates were 23.1 (2000) and 24.6 (2006); fewer than 1 in 200 KD
cases were reported to VAERS.
It is bewildering, therefore,
to learn
that FDA and CDC officials used VAERS data to dismiss a placebo-controlled
trial that found a 5-fold KD risk associated with RotaTeq--RR=4.9; 95% CI
0.6, 239. (Pediatr Infect Dis J 28:943, 2009.
risk
associated with RotaTeq would translate to an extra 4000 U.S. cases
annually
in young children.
I know that this discussion began with
febrile
convulsions in young children given seasonal flu vaccine, but the problems
with voluntary reporting systems, underreporting of adverse events and the
way the data are used by public health officials and the vaccine industry
apply
to other vaccines and other serious clinical problems. How can public
health
officials rely on a system that reports fewer than 1% of adverse effects?
How
can they dismiss placebo-controlled trials that raise serious
possibilities of
vaccine-caused illness?
Competing interests:
None declared
Competing interests: No competing interests
In our recent letter and rapid response (1,2) we pointed out that in Australia serious adverse reactions occurred at very high rates in young children who received the latest seasonal influenza vaccine containing the H1N1 antigen (1 per 110 had febrile convulsion). We also noted that fever is the important predisposing factor in febrile convulsions and that fevers were common in children in an Australian H1N1 vaccine study done prior to the approval of the latest influenza vaccines by regulatory authorities.
Our letter, however, met with disapproval from Isaacs et al, Lopert and Nolan, and Durrheim (3-5) (some of whom are from or associated with the Australian regulator (TGA), CSL H1N1 influenza vaccine studies, and/or are on Australian national immunisation committees). We were criticized for making a "careless connection" by considering the results of a study of monovalent H1N1 influenza vaccine (which found three to six in ten children developed fever following vaccination) in light of the current suspension of trivalent influenza vaccine in children under 5 in Australia. However we did not claim that specific trials made future events predictable with 100% accuracy; rather, we highlighted the apparent lack of concern over high rates of fever in the way the data were reported by authors and handled by regulators in their approval of the vaccine. And in light of a poor evidence base of largely inadequately powered studies to assess the safety and efficacy of influenza vaccines overall, and particularly in children, we argued that problems like those witnessed in Australia do not seem particularly surprising.
We agree with Durrheim (5) that a passive adverse event surveillance system detected signals that eventually led to the suspension of influenza vaccine in children. But the signal was especially strong in this case, and begs the question of what signals we might be missing. Consider Lopert and Nolan's (4) use of passive surveillance system data to state that monovalent H1N1 vaccine has a low harms profile. They state that of over 370,000 doses of Panvax Junior distributed in Australia to date, there have been "only 16 cases" of febrile convulsion (4). They also state: "In the US double blind placebo-controlled trial, which evaluated doses of 7.5μg and 15μg, only 1.9% of children under 3 in the 7.5μg group experienced moderate fever and the same proportion a severe fever". This means that although we can reasonably expect that 3.8% of children (1.9% + 1.9%), or 14,000 children, would have had moderate to severe fevers following vaccination (>38.5 °C), in reality only 129 (or less than 1%) were registered in TGA‘s passive surveillance system (6). Rather than demonstrating adequate safety, their example demonstrates the gross inadequacy of the Australian passive surveillance system to find the true numbers of adverse reactions, even when they are as simple to measure as a high fever.
Based on trial data, we can expect that a large proportion of young children will develop fevers and influenza-like symptoms after receiving influenza vaccines (e.g. for the Glaxo vaccine, fever in 43% of children under 3 years (7) and, for the 15μg dose of monovalent CSL H1N1 influenza vaccine, fever in 35.4% (8). This is a higher proportion of children than those likely to develop symptomatic influenza each year. Thus, we reiterate our view that the current evidence suggests that influenza vaccines in young children without risk factors are likely to do more harm than good (1,2). When you take into account the unpredictability but apparent increased rates of serious adverse reactions such as febrile seizures that occurred in Australia in young children, the balance tilts even more such that overall, influenza vaccine in children is causing more harm than good.
While Isaacs et al, Lopert and Nolan, and Durrheim (3-5) have said or implied that the "benefits and risks continues to strongly favour influenza immunisation for children aged under 5 years" (5), it is worth noting that the Australian government and regulator (TGA) have recommended that seasonal influenza vaccination remain suspended in young children without risk factors (9). We agree and believe it should not be reintroduced for these children until good quality prospective studies evaluating safety and efficacy in large numbers of children have been performed. So far, these types of studies are not available (10).
We need to always ensure any mass vaccination campaign does more good than harm. We need trials of vaccines or their components with meaningful outcomes (i.e. clinical outcomes) as opposed to having only relatively poor surrogates such as antibody responses. Seasonal influenza vaccines can change every year in their composition. This is why we also need large active surveillance systems in place to assess whether variations in the vaccine components induce unexpected higher rates of adverse reactions. Passive surveillance will always grossly underestimate adverse reaction rates.
Peter Collignon, Peter Doshi, Tom Jefferson
References
1. Collignon P, Doshi P, Jefferson T. Ramifications of adverse events in children in Australia. BMJ. 2010 Jun 9;340(jun09_3):c2994. http://www.bmj.com/cgi/content/full/340/jun09_3/c2994
2. Collignon P, Doshi P, Jefferson T. Adverse events following influenza vaccination in Australia—should we be surprised? BMJ Rapid Response (May 7, 2010) http://www.bmj.com/cgi/eletters/340/may04_2/c2419#235364.
3. Isaacs D, Macartney K and McIntyre P. Benefits and risks of childhood influenza vaccination. BMJ Rapid Response (June 28, 2010) http://www.bmj.com/cgi/eletters/340/jun09_3/c2994#237918
4. Lopert R and Nolan T. Panvax ADRs not a predictor. BMJ Rapid Response (June 28, 2010) http://www.bmj.com/cgi/eletters/340/jun09_3/c2994#237926
5. Durrheim DN. Importance of post-marketing surveillance. BMJ Rapid Response (July 4, 2010) http://www.bmj.com/cgi/eletters/340/jun09_3/c2994#238271
6. Suspected adverse reactions to Panvax® reported to the TGA 30 September 2009 - 30 April 2010. Department of Health and Aging. Therapeutic Goods Administration (TGA). http://www.tga.gov.au/alerts/medicines/h1n1vaccine1.htm
7. Product Information. Pandemrix-H-C-832-IA-40G GlaxoSmithKline. (April 15, 2010) http://www.ema.europa.eu/humandocs/PDFs/EPAR/pandemrix/emea-combined-h83...
8. Nolan T, McVernon J, Skeljo M, Richmond P, Wadia U, Lambert S, et al. Immunogenicity of a Monovalent 2009 Influenza A(H1N1) Vaccine in Infants and Children: A Randomized Trial. JAMA. 2010 Jan 6;303(1):37-46. http://jama.ama-assn.org/cgi/content/full/303/1/37 and Supplementary online content. http://jama.ama-assn.org/cgi/content/full/2009.1911/DC1
9. Bishop J. Seasonal flu vaccine remains suspended for young children without risk factors. DoHA, Canberra, 1st June, 2010. Link: http://www.health.gov.au/internet/main/publishing.nsf/Content/mr-yr10-de...
10. Jefferson T, Rivetti A, Harnden A, Di Pietrantonj C, Demicheli V. Vaccines for preventing influenza in healthy children. Cochrane Database Syst Rev. 2008;(2):CD004879. http://www3.interscience.wiley.com/homepages/106568753/CD004879_standard...
Competing interests:
TJ is author of the relevant Cochrane reviews.
Competing interests: No competing interests
It is concerning that a careless connection between febrile
convulsions associated with the 2010 trivalent seasonal influenza vaccine
in Australian children under five years of age and Australian trial data
for the 2009 monovalent pandemic influenza vaccine, which has not been
associated with excess febrile convulsions, was reported.(1) Allegations of collusion between regulators and vaccine manufacturers in suppressing
vaccine safety profiles were inferred but unsubstantiated.(1,2)
Unfortunately in future years parents seeking reassurance about the
general safety of childhood vaccines on the worldwide web, may place their
children at risk of potentially life-threatening vaccine-preventable
diseases after encountering this contentious letter raising doubts about
the commitment of vaccine regulators to protecting children.
It would have been more constructive for the authors to emphasise the
importance of vaccine post-marketing surveillance.(3) As demonstrated by
the recent Australian experience, passive adverse events monitoring
successfully detected a signal that resulted in an appropriate rapid
suspension of a product while rigorous epidemiological and laboratory
investigations were conducted. However, there is scope to explore new
systems of post-marketing surveillance to monitor introduction of new
vaccines at population level. This could be done by engaging and enrolling
vaccinees or their parents in on-line reporting that is electronically
prompted at various intervals post-vaccination in countries with high
internet coverage. Not only could this provide more rapid and complete
reporting of safety signals requiring careful interrogation, but it may
also provide the elusive “vaccines administered” denominator essential for
interpreting rates of reported adverse events.
References
1) Collignon P, Doshi P, Jefferson T. Ramifications of adverse events in
children in Australia. BMJ 2010;340:c2994
2) Collignon P, Doshi P, Jefferson T. Rapid response. Adverse events
following influenza vaccination in Australia—should we be surprised? Link:
www.bmj.com/cgi/eletters/340/may04_2/c2419#235364.
3) Global Advisory Committee on Vaccine Safety, 3–4 December 2009. Weekly
Epidemiological Record 2010, 85, 29–33.
Competing interests:
None declared
Competing interests: No competing interests
In noting that fever is the most important risk factor for febrile
convulsions, Collignon et al imply that rates of fever reported in young
children in a preregistration clinical trial of CSL’s monovalent pandemic
H1N1 vaccine (Panvax) were an important but overlooked predictor of the
increased rates of fever and febrile convulsions recently reported
following administration of CSL’s 2010 southern hemisphere seasonal
trivalent influenza vaccine (TIV), Fluvax, and which have led to the
suspension of TIV use in children under five.
Despite the claim that “… a large proportion of children developed
fevers after vaccination”, the vast majority of febrile reactions reported
in the Australian paediatric trial of Panvax (1) were in fact mild
(≤38.5˚C), with only 8/367 (2%) children experiencing a severe
fever (>39.5˚C) following the first dose of vaccine. Moreover the
occurrence of fever was clearly dose-related, and the figures quoted
include results for subjects who received 30µg, twice the dose of H1N1
antigen in both Panvax and Fluvax, and 4-times the dose in Fluvax Junior.
In the 15µg group, severe fever post dose 1 was reported in only one child
under 3, and none was reported in those 3 years and older. In the US
double blind placebo-controlled trial (2), which evaluated doses of 7.5µg
and 15µg, only 1.9% of children under 3 in the 7.5µg group experienced
moderate fever and the same proportion a severe fever. Further, in
children aged 3 and older, rates of fever in the 7.5µg group were similar
to placebo and severe fever was reported in neither the 7.5µg nor 15µg
groups.
More important is the recognition that with more than 8.7 million
doses of Panvax and over 370,000 of Panvax Junior distributed in Australia
to date, there have been only 16 cases of febrile convulsions in children
reported to the Therapeutic Goods Administration (TGA). This is consistent
with rates of febrile convulsions seen with previous seasonal TIV, and
further challenges the claim that the unusual pattern of adverse reactions
following 2010 TIV should have been anticipated from the clinical trials
of the monovalent vaccine.
The investigation into the increased rate of febrile reactions
associated with 2010 seasonal TIV is ongoing and has thus far failed to
identify its biological basis. In the interim, focusing on rates of fever
in trials of the monovalent vaccine is potentially misleading. In
Australia in 2009, 877 children under the age of 5 were admitted to
hospital with pandemic influenza-related illness, 29 to intensive care and
4 died (3). In light of the significant paediatric morbidity and mortality
recorded here and elsewhere (4) post pandemic H1N1 infection, and the very
low rates of significant febrile reactions following monovalent H1N1
vaccine, the statement that “… such a high proportion of children develop
moderate to severe febrile reactions to the (seasonal) influenza vaccine,
more harm than good seems likely from vaccinating them” seems a
regrettable miscalculation of the risks and benefits.
Ruth Lopert1, Principal Medical Adviser, Terry Nolan2, Head,
Melbourne School of Population Health
1 Therapeutic Goods Administration, Symonston ACT 2609, Australia, 2
University of Melbourne and Murdoch Children’s Research Institute,
Parkville Victoria 3010, Australia.
References
1. Nolan T, McVernon J, Skeljo M, Richmond P, Wadia U, Lambert S
et al. Immunogenicity of a monovalent 2009 influenza A(H1N1) vaccine in
infants and children: a randomized trial. JAMA 2010;303:37-46.
Supplementary online content: http://jama.ama-
assn.org/cgi/content/full/2009.1911/DC1
2. World Health Organisation 6th meeting on evaluation of
pandemic influenza vaccines in clinical trials, February 2010, Geneva,
Switzerland.
http://www.who.int/vaccine_research/diseases/influenza/meeting_18_19Feb2...
3. Office for Health Protection, Department of Health and Ageing,
Australia.
4. Fluview report, 2009-2010 Influenza Season Week 20 ending May
22, 2010. Centers for Disease Control and Prevention.
http://www.cdc.gov/flu/weekly
Competing interests:
TN was chief investigator on the CSL Ltd sponsored trial of the pandemic H1N1 vaccine in Australian children. He has received travel assistance from WHO and CSL Ltd to present the data on this and other H5 influenza vaccine studies at World Health Organisation scientific meetings.
Competing interests: No competing interests
When doctors are prepared to be cavalier with data, the anti-
immunisation lobby needs look no further for ammunition [1]. Collignon et
al, in stating that less than one in a million Australian children died
from pandemic H1N1 influenza last winter neglect to mention that children
aged 0-4 years old had the highest incidence of hospital admission in
2009. Overall, 1,000 of the approximate population of 4 million Australian
children under 15 years old were admitted to hospital with proven pH1N1
influenza last winter and 11 died [2].
Febrile convulsions occur in some 3% of normal children by 5 years of
age and do not cause lasting neurological damage [3]. On the other hand,
influenza infection may be the precipitating cause of a febrile convulsion
in up to 1 in 5 children admitted to hospital [4]. Previous studies have
not found any excess febrile convulsions associated with influenza
vaccine, although fever is well recognised to occur following the first
dose in young children [5]. In Australia in 2010, febrile convulsions
occurred in approximately 0.9% of children less than 3 years old receiving
the CSL seasonal trivalent influenza vaccine but .the monovalent pandemic
H1N1 vaccine, also made by CSL, was not associated with excess febrile
convulsions [6]. This is in stark contrast to the extrapolations made by
Collignon et al from a clinical trial of this monovalent vaccine [1]. As a
precautionary measure, routine immunisation of children under 5 years old
with the 2010 seasonal vaccine was suspended, but continued with the
monovalent pandemic H1N1 vaccine. For an individual child at increased
risk of severe complications of influenza infection, it was recommended to
assess the risks and benefits of trivalent vaccine[6].
Although Jefferson et al have queried the ethics of some influenza
vaccine publications, their rationale is unclear. First, there is good
evidence that influenza vaccine is immunogenic in children and that
immunisation of children provides herd immunity to those around them [7].
Second, the overall safety record of influenza vaccines in children is
good [5]. The benefits are particularly marked for children with medical
conditions predisposing them to severe influenza, who are five times more
likely to be hospitalised than healthy children [5]. Our analysis of
benefits and risks continues to strongly favour influenza immunisation for
children aged under 5 years.
References
1) Collignon P, Doshi P, Jefferson T. Rapid response. Adverse events
following influenza vaccination in Australia—should we be surprised? Link:
www.bmj.com/cgi/eletters/340/may04_2/c2419#235364.
2) Australian Government Department of Health and Ageing. Australia
Influenza Surveillance. Link:
http://www.health.gov.au/internet/healthemergency/publishing.nsf/Content...
(accessed 24.6.10)
3) Verity CM, Greenwood R, Golding J. Long-term intellectual and
behavioral outcomes of children with febrile convulsions. N Engl J Med
1998; 338: 1723-8.
4) Kwong KL, Lam SY, Que TL, Wong SN. Influenza A and febrile
seizures in childhood. Pediatric Neurology 2006; 35: 395-9.
5) Fiore AE, Shay DK, Broder K et al. Prevention and control of
seasonal influenza with vaccines: recommendations of the Advisory
Committee on Immunization Practices (ACIP), 2009. Morbidity &
Mortality Weekly Report. Recommendations & Reports 2009; 58: 1-52.
6) Bishop J. Seasonal flu vaccine remains suspended for young
children without risk factors. DoHA, Canberra, 1st June, 2010. Link:
http://www.health.gov.au/internet/main/publishing.nsf/Content/mr-yr10-dept
-dept010610.htm.
7) Loeb M, Russell ML, Moss L. Effect of Influenza Vaccination of
Children on Infection Rates in Hutterite Communities. JAMA 2010; 303: 943-
50.
Competing interests:
None declared
Competing interests: No competing interests
Cunningham poignantly asks, "Do all vaccines save so many lives, so much misery, and so much money that obscuring the adverse effects is ethically justified?" [1] The situation, however, is even worse than Cunningham portrays. Influenza vaccine licenses are not granted on real outcomes (i.e. demonstrated field outcomes such as a reduction in morbidity, hospitalization, or mortality) but instead on surrogate outcomes--namely antibody titre rises--and no one knows their relationship to field effectiveness. [2]
References
1. Cunningham AS. Fever, convulsions, vaccines and...Kawasaki Disease? BMJ Rapid Response. 2010 Jun 11 [cited 2010 Jun 14]; Available from: http://www.bmj.com/cgi/eletters/340/jun09_3/c2994#237061
2. Subbarao K, Joseph T. Scientific barriers to developing vaccines against avian influenza viruses. Nat Rev Immunol. 2007 Apr;7(4):267-278.
Competing interests:
We are authors of the original letter.
Competing interests: No competing interests
The H1N1 vaccine study discussed by Collignon et. al. (JAMA 303:37,
2010)
reported a Kawasaki-like syndrome in a 2 year-old boy 4 days after
receiving
a 30 microgram dose of the vaccine, but the authors stated that this
"...adverse event of special interest was considered unrelated to the
vaccine."
In another trial one of 201 infants 6-12 weeks old developed Kawasaki
Disease after receiving seasonal flu vaccine (TIV) along with regularly
scheduled vaccines. This case also was considered "...unrelated to
vaccines."
(Pediatr ID Journal 28:1099, 2009)
Vaccine developers, the FDA and
the
CDC seem to be doing their best to obscure any links between vaccines and
serious adverse effects like KD. In a Vaccine Safety Datalink study
Prevnar
was associated with a 3-fold risk of KD, but after adjustment the
association
became statistically non-significant, P= 0.083. (Pediatr ID Journal
28:438,
2009) In June, 2007 we were alerted by the FDA to the possibility that
RotaTeq was associated with a 5-fold risk od KD, P=0.10. VAERS data were
later used by the FDA and the CDC to conclude, "Our review does not
suggest
an elevated KD risk for RotaTeq or other vaccines." (Pediatr ID Journal
28:943,
2009)
VAERS vastly underreports adverse events; for example the
U.S.
background rate of children under 5 is at least 12-14 per 100,000 child-
years.(Pediatrics 109:e87, 2002) The KD rate derived from VAERS reports
was
0.12 per 100,000 child-years!!! Incidentally, the KD rate in Prevnar
recipients
was 36 per 100,000 child-years, and during the 6 weeks of the RotaTeq
trial
there were 5 cases of KD in 36,150 vaccine recipients, a rate of 120 cases
per
100,000 child-years!
Parenthetically, KD is still a mystery
disease,
cause unknown. It was first reported in 1976 and its frequency since then
has progressively increased in North America, Europe and Japan.
Vaccine
research suffers from the same deep flaw that we find in drug/device
research: licenses are granted based on studies that are too small to
detect
serious effects, whose detection are then left to "post-marketing
surveillance"
which is generally capricious or mythical. Is it cynical to suggest that
this is
no accident, that the manufacturers--with the consent of medical
scientists
and public health officials--depend on small sample sizes and defective
reporting systems to subvert the detection of uncommon but serious adverse
effects? Do all vaccines save so many lives, so much misery, and so much
money that obscuring the adverse effects is ethically justified?
In a
recent trial Prevnar-13 was given to 122 infants along with their
regularly
scheduled vaccines. No cases of KD were reported, but 20% developed fever
(3% had temperatures >39 degrees C.) and 80% developed one or more
systemic symptoms after the vaccinations. (Pediatrics 124:866, 2010) How
many febrile convulsions and how many cases of KD will occur after the
vaccine is marketed? Will we ever know? Do we care?
Allan S.
Cunningham, retired pediatrician, Cooperstown NY
cunningham386@yahoo.com>
Competing interests:
None declared
Competing interests: No competing interests
Cobblers and Porkies.
Dear Sir,
Given that the Australian death toll from ordinary flu in Australia
is purported to be 2,500 per year (1), perhaps the following information
puts H1N1 reality into perspective:
“As at 18 December 2009, there have been 37,537 confirmed cases of
pandemic (H1N1) 2009 and 191 deaths reported in Australia.” (2)
It could be argued, as it has been elsewhere in BMJ, that H1N1 was
far more effective than any possible influenza vaccine could be, in
reducing deaths from influenza. (3)
It could also be argued that annual influenza vaccines haven't
reduced Australia's annual flu death toll at all.
Perhaps the TGA might also like to discuss the percentage of this tiny
number of H1N1 deaths, with identifiable risk factors or co-morbidities,
which in this country, appear to have been more than a significant
mortality contribution, in what has otherwise been a miniscule death toll
compared to the numbers which the medical profession rumbles out in the
pamphlets, posters and media every year.
It could however, be the case, that "normal" case numbers might
actually be spurious. Perhaps they are primarily a political construct in
order to bolster vaccine sales for a disease which death statistics show,
continues to be unperturbed by the vastly increasing sales of flu
vaccines.
It won't have escaped those who read the recent innocently titled
article on influenza called "Influenza vaccination and mortality benefits:
New insights, new opportunities" (4), that Simonsen continues to hit the
nail on the head.
No doubt mindful that criticising any vaccine often leads to being
dubbed anti vaccine (5), which narrows available funding, she goes to
great pains to discuss better vaccines, while reinforcing the fact that
the current ones leave more than a lot to be desired.
Isn't it time actually discuss the white elephant in the room, rather
than throw more words at a policy for the sake of shoring up the
unsatisfactory?
To infer that questioning vaccine safety is propping up the anti-
vaccine position is strange. The anti-vaccine movement need only refer
people to the fact that the medical profession continues to ignore
Simonsen's articles, and Cochrane Reviews, and whatever other pieces of in
-your-face medical evidence there are, as well as people's own
experiences.
Denial in the face of the blindingly obvious is not only an own goal,
but also leads people to ask what other own goals have been carefully
concealed.
Hilary Butler.
(1)http://humanswineflu.health.vic.gov.au/ Victorian Government
Health Information, H1N1 Influenza 09 page
(2)
http://www.health.gov.au/internet/healthemergency/publishing.nsf/Content...$File/ozflu
-no32-2009.pdf Australian Influenza Summary Surveillance Report No 32,
2009.
(3) http://www.bmj.com/cgi/content/extract/339/sep29_3/b3959 Law R,
2009. “By any maths would be as weak” BMJ 2009;339:b3959
(4) http://www.ncbi.nlm.nih.gov/pubmed/19840664 Simonsen L, et al,
2009. “Influenza vaccination and mortality benefits: new insights, new
opportunities” Vaccine, Oct 23;27(45):6300-4.
(5)http://www.bmj.com/cgi/eletters/340/jun29_4/c3508 Ganapati Mudur,
2010 , “Antivaccine lobby resists introduction of Hib vaccine in India”
BMJ 2010; 340: c3508
Competing interests:
None declared
Competing interests: No competing interests