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  <xs:element id="biib_GovernmentSecuritiesNonCurrentMember" abstract="true" name="GovernmentSecuritiesNonCurrentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="biib_PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain" abstract="false" name="PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="biib_FumarateMember" abstract="true" name="FumarateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="biib_AducanumabMember" abstract="true" name="AducanumabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="biib_SangamoTherapeuticsInc.AgreementMember" abstract="true" name="SangamoTherapeuticsInc.AgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="biib_PlanAssetsForDeferredCompensationFairValueDisclosure" abstract="false" name="PlanAssetsForDeferredCompensationFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
