<?xml version="1.0" encoding="utf-8"?>
<!--Generated by DFIN XBRL Instance Document - http://www.dfinsolutions.com/ - Version R3.0 - on 01-July-2024 [09:12:53] {PM}-->
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<annotation>
<appinfo>
<link:roleType roleURI="http://www.jhinvestments.com/role/N2FeeTable" id="N2FeeTable">
<link:definition>1001 - Disclosure - N-2 - [Fee Table]</link:definition>
<link:usedOn>link:presentationLink</link:usedOn>
<link:usedOn>link:definitionLink</link:usedOn>
<link:usedOn>link:calculationLink</link:usedOn>
</link:roleType>
<link:roleType roleURI="http://www.jhinvestments.com/role/N2InvestmentObjectives" id="N2InvestmentObjectives">
<link:definition>1002 - Disclosure - N-2 - [Investment Objectives]</link:definition>
<link:usedOn>link:presentationLink</link:usedOn>
<link:usedOn>link:definitionLink</link:usedOn>
<link:usedOn>link:calculationLink</link:usedOn>
</link:roleType>
<link:roleType roleURI="http://www.jhinvestments.com/role/N2SharePriceTable" id="N2SharePriceTable">
<link:definition>1003 - Disclosure - N-2 - [Share Price Table]</link:definition>
<link:usedOn>link:presentationLink</link:usedOn>
<link:usedOn>link:definitionLink</link:usedOn>
<link:usedOn>link:calculationLink</link:usedOn>
</link:roleType>
<link:roleType roleURI="http://www.jhinvestments.com/role/N2OutstandingSecurities" id="N2OutstandingSecurities">
<link:definition>1004 - Disclosure - N-2 - [Outstanding Securities]</link:definition>
<link:usedOn>link:presentationLink</link:usedOn>
<link:usedOn>link:definitionLink</link:usedOn>
<link:usedOn>link:calculationLink</link:usedOn>
</link:roleType>
<link:linkbaseRef xlink:type="simple" xlink:href="cik0000925683-20240628_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
<link:linkbaseRef xlink:type="simple" xlink:href="cik0000925683-20240628_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
<link:linkbaseRef xlink:type="simple" xlink:href="cik0000925683-20240628_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
</appinfo>
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<import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
<import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
<import namespace="http://xbrl.sec.gov/dei/2023" schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd" />
<import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd" />
<import namespace="http://xbrl.sec.gov/cef/2023" schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023.xsd" />
<import namespace="http://xbrl.sec.gov/cef-pre/2023" schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023_pre.xsd" />
<element name="CommonSharesMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="cik0000925683_CommonSharesMember" substitutionGroup="xbrli:item" />
</schema>
