Grading System for Recommendations
Category of Evidence
Ia
Ib
IIa
IIb
III
IV
Strength of Recommendation
Evidence from meta-analysis of
randomized controlled trials
Evidence from at least one
randomized controlled trial
Evidence from at least one
controlled study without
randomization
Evidence from at least one other
type of quasiexperimental study
Evidence from nonexperimental
descriptive studies, such as
comparative studies
Evidence from expert committee
reports or opinions or clinical
experience of respected
authorities or both
A
Directly based on category I evidence
B
Directly based on category II evidence
or extrapolated recommendation from
category I evidence
C
Directly based on category III evidence
or extrapolated recommendation from
category I or II evidence
Directly based on category IV evidence
or extrapolated recommendation from
category I, II, or III evidence
D
Abbreviations
DT, diphtheria and tetanus toxoids (pediatric formulation); DTaP, diphtheria and tetanus toxoids
and acellular pertussis (pediatric formulation); Hib, Haemophilus influenzae type B; HPV, human
papillomavirus; MMRV, measles, mumps, rubella and varicella; Td, tetanus and diphtheria toxoids (adult/
adolescent formulation); Tdap, tetanus and diphtheria toxoids and acellular pertussis (adult/adolescent
formulation)
Source
Kelso JM, Li JT, Nicklas RA, et al. Adverse reactions to vaccines. Ann Allergy Asthma Immunol.
2009;103(4 Suppl 2):S1-S14.
Disclaimer
This Guideline attempts to define principles of practice that should produce high-quality patient care. It focuses
on the needs of primary care practice, but also is applicable to providers at all levels.
This Guideline should not be considered exclusive of other methods of care reasonably directed at obtaining the
same results. The ultimate judgment concerning the propriety of any course of conduct must be made by the
clinician after consideration of each individual patient situation.
Neither IGC, the medical associations, nor the authors endorse any product or service associated with the
distributor of this clinical reference tool.
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