Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Catch-up and high-risk vaccination
Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Unprotected high-risk child after exposure
A child with severe immunosuppression, asplenia, complement blockade or another major vulnerability may remain susceptible despite previous vaccination. Significant exposure to measles, varicella, meningococcal disease, hepatitis or rabies can require time-critical prophylaxis, testing or antimicrobial treatment.
Action: Obtain exact exposure time, vaccine and disease history, immune condition and current medicines; contact paediatric infection, the responsible specialist and health protection immediately. Use the disease-specific national post-exposure pathway rather than giving a contraindicated live vaccine or assuming prior vaccination guarantees protection. Treat any fever or systemic illness as a separate urgent clinical problem.
Role and principles
Construct a safe minimum-visit catch-up plan for an incomplete or uncertain history and add current risk-based vaccines for children with asplenia, complement disorders, immunosuppression or other vulnerable conditions.
Catch-up vaccination restores protection after delay, migration, disrupted care, vaccine hesitancy, school absence or uncertain records. The goal is valid immunity as quickly as possible, not replication of every visit that would have occurred in infancy.
Begin by reconstructing the history from child-health records, GP and school systems, prior providers, overseas documents and a reliable detailed verbal history. Record the evidence supporting each accepted dose rather than marking the entire course simply complete.
A valid completed primary course is not restarted after a long gap because immune memory persists. Continue from the last valid dose, respecting minimum ages, minimum intervals and product-specific rules.
When no adequate history exists, assume unimmunised. Extra doses of most inactivated vaccines are generally safer than leaving a susceptible child, although tetanus- or diphtheria-containing products can cause greater local reactions after repeated doses.
Practice
Two practice questions
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Question 1 of 2
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Paediatrics and child healthOriginal SBA
Interrupted primary course
A 6-year-old has reliable documentation of two valid infant 6-in-1 doses but then received no further vaccination for several years. What is the correct catch-up principle?
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
UKHSA pneumococcal clinical-risk programmeCurrent 2026 PCV20 transition and special schedules for children with asplenia, complement disorder or severe immunocompromise.
Administer vaccines due together at separate sites. The UKHSA catch-up tables deliberately compress the plan into visits separated by minimum intervals; unnecessary spacing prolongs risk and increases loss to follow-up.
Age determines product. Children under 10 generally use a DTaP-containing combined product for primary catch-up, while those from the 10th birthday use Td/IPV. Product selection must also preserve Hib and hepatitis B coverage where required.
Live-virus catch-up has age and immune constraints. Doses of measles-, mumps-, rubella- or varicella-containing vaccine before 12 months do not count toward the routine course, and the two valid doses are normally at least 4 weeks apart.
Rotavirus is an exception to the principle that late is better than never. The first dose must be given before 15 weeks and the course completed before 24 weeks, with additional contraindications including SCID and previous intussusception.
High-risk vaccination is additive: complete routine protection first, then add vaccines or doses required by the condition. The exact schedule depends on age at diagnosis, previous vaccines, immune function and imminent treatment.
Asplenia, splenic dysfunction and haemoglobinopathies increase overwhelming infection from encapsulated bacteria. MenACWY, MenB, risk-specific pneumococcal vaccination and annual influenza are important, but breakthrough infection remains possible.
Terminal complement deficiency and complement inhibitors create particularly high meningococcal risk. MenACWY and MenB should ideally precede therapy by at least 2 weeks; when treatment starts sooner, national guidance adds antibiotic prophylaxis until 2 weeks after vaccination.
The 2026 pneumococcal programme uses PCV20 for high-risk groups as supply transitions. Children under 2 with asplenia, complement disorder or severe immunocompromise follow a special PCV20 schedule rather than the ordinary PCV13 timing; use the current table.
Other clinical risk groups include chronic respiratory, heart, kidney, liver or neurological disease, diabetes, cochlear implant and immunosuppression. Annual influenza and pneumococcal protection are common requirements, while hepatitis, meningococcal and other vaccines depend on the specific risk.
Inactivated vaccines cannot replicate and are generally safe during immunosuppression, although response may be reduced and revaccination may be needed. Live vaccines can replicate extensively and require specialist permission and treatment-specific timing.
Healthy household contacts should be fully immunised, including relevant influenza and varicella protection, to reduce exposure. Specific contact precautions apply after some live vaccines, so follow the Green Book rather than withholding all live products.
Every plan needs ownership: list products and dates, who will administer them, next appointments, specialist responsibilities and how the family will act after exposure or fever. A plan without recall is not a completed intervention.
Key points
Without a documented or reliable verbal history, assume the child is unimmunised and plan an age-appropriate full course while continuing to retrieve records.
Never restart a valid vaccine course solely because the interval is long; resume it and complete the missing doses.
Combine compatible vaccines into the minimum number of visits and shortest valid timescale, usually with 4 weeks between early catch-up visits.
A child entering the UK part-way through a course transfers to the UK schedule; assess each overseas dose by age, product, date and interval.
From 8 weeks to the first birthday, a basic three-visit course uses 6-in-1 each visit, MenB and rotavirus at visits 1 and 2 when age-eligible, and PCV13 at visit 3.
From the first to second birthday, visit 1 can include 6-in-1, PCV13, MenB and MMRV; repeat 6-in-1 and MenB at visit 2 and 6-in-1 at visit 3, then complete age-specific boosters.
From age 2 to under 10, use three age-appropriate DTaP/IPV/Hib/HepB-containing doses and two MMR or MMRV doses at least 4 weeks apart, then restore preschool boosters as specified.
From the 10th birthday, use three Td/IPV doses, two MMR doses and MenACWY, then add HPV and later boosters according to age and previous valid doses.
MMR or MMRV doses given before the first birthday do not
Assessment and patient selection
Classify record certainty
Separate documented valid doses, reliable detailed history, unverifiable recollection and genuinely absent information before constructing the schedule.
Validate each dose
Check product, disease antigens, age administered, interval, route when relevant and whether an overseas product is equivalent.
Identify age pathway
Use under 1, 1 to under 2, 2 to under 10 and 10-plus catch-up tables, then account for cohort transitions.
Identify clinical risk
Ask about spleen, complement, transplant, cancer, immune disease, medicines, cochlear implant and chronic organ disease.
Map treatment timing
Record planned surgery, chemotherapy, biologic infusion, transplant and steroid exposure because timing changes safety and immune response.
Assess exposure urgency
Ask about recent measles, varicella, meningococcal, hepatitis or travel exposure before treating catch-up as a routine administrative task.
Red flags requiring action
Fever or systemic illness in a child without a functioning spleen, receiving complement inhibition or severely immunosuppressed requires urgent clinical assessment even when vaccinations are complete.
Never give a live vaccine to a severely immunosuppressed child without explicit specialist confirmation that immune status and timing permit it.
Baseline assessment
01First-line: record reconciliationFirst stepFirst line
Why
Establish the number and validity of previous doses.
Interpretation and limitations
Use linked NHS and child-health systems, school records, the red book and legible overseas evidence; document why a verbal history is considered reliable or insufficient.
02Age and minimum-interval calculation
Why
Build the shortest valid series without invalid early doses.
Interpretation and limitations
Apply the current UKHSA age table and disease chapter. Long gaps do not invalidate earlier doses, but too-short intervals may require an additional dose.
03Immune and treatment review
Why
Determine live-vaccine safety and likely response to inactivated products.
Interpretation and limitations
Use diagnosis, specialist letters, transplant or chemotherapy phase, biologic agent, steroid dose and timing; blood counts alone do not provide universal live-vaccine clearance.
04Selective serology
Why
Resolve a small number of antigen-specific questions or document response in specialist pathways.
Interpretation and limitations
Routine catch-up does not require antibody testing. Use hepatitis B, varicella or other serology only when the Green Book or responsible specialist specifies an actionable result.
Interventions
01Unknown historyAssume susceptible and compress safelyFirst stepNo documented or sufficiently reliable vaccine history can be obtained.+
1Classify the child by exact age, date of birth and clinical risk, and continue urgent record retrieval without postponing indicated protection.
2Use the current UKHSA catch-up table to place all compatible visit-1 vaccines at separate sites, observing rotavirus, live-vaccine and immune restrictions.
3Book visits 2 and 3 at the minimum valid intervals, record each product immediately and add age-specific boosters, HPV, influenza and selective vaccines.
02Incomplete courseResume rather than restartAt least one previous dose is valid but the recommended series was not completed.+
1Validate every recorded dose by age, product and interval and identify antigens still missing rather than counting visits alone.
Medicines and treatment safety
Provides rapid age-appropriate primary catch-up across the antigens most likely to be missing.
Under-10 catch-up primary course
Use 3 visits usually 4 weeks apart. Under 1 year: 6-in-1 each visit, MenB and rotavirus at visits 1 and 2 when age-eligible, PCV13 at visit 3. Age 1 to under 2 adds PCV13, MenB and MMRV at visit 1. Age 2 to under 10 uses 6-in-1 and MMR or MMRV at visits 1 and 2, then 6-in-1 at visit 3.
Use the current UKHSA table and product footnotes. Observe rotavirus upper ages, SCID and intussusception restrictions, live-vaccine contraindications, minimum intervals and the need for later boosters.
Give Td/IPV at 3 visits usually 4 weeks apart, MMR at visits 1 and 2 at least 4 weeks apart, and MenACWY at visit 1; add HPV, influenza and later Td/IPV boosters according to age, risk and valid previous doses.
Do not use a paediatric pertussis combination by habit after the 10th birthday. Account for valid overseas doses and live-vaccine immune or pregnancy restrictions.
Adds protection against encapsulated bacteria in children with markedly increased invasive-disease risk.
High-risk pneumococcal and meningococcal vaccines
Use the current Green Book age-and-history schedule. Children with asplenia, complement disorder or severe immunocompromise may require PCV20 from infancy; asplenia and complement risk also require MenACWY and MenB, ideally at least 2 weeks before planned intervention.
Targets, monitoring and follow-up
Maintain one reconciled schedule showing accepted previous doses, doses given today, minimum next dates and the service responsible for each appointment.
Use active recall after every missed visit and communicate across GP, child-health, school and specialist systems to prevent duplicated or omitted courses.
Review vaccine response only when a disease-specific or specialist pathway makes the result actionable; do not order broad antibody panels routinely.
After transplantation, chemotherapy or B-cell-depleting treatment, obtain the specialist revaccination plan and do not assume pre-treatment immunity remains adequate.
Reassess risk-based eligibility when diagnosis, splenic function, medicines or treatment phase changes and during every annual influenza campaign.
Provide written fever and exposure plans to high-risk families, including the emergency route and confirmation that vaccination does not eliminate invasive infection.
Document adverse events and administration errors, seek programme advice when dose validity is uncertain and report appropriate suspected reactions through Yellow Card.
Special situations
Long gaps do not erase doses
A valid priming dose still counts after delay, so continue the series instead of exposing the child to an unnecessary restart.
Short intervals can invalidate
Catch-up is fast but not arbitrary; age and minimum intervals preserve immunogenicity and determine whether another dose is needed.
Rotavirus cannot wait indefinitely
Strict upper ages make early identification essential; it is not a vaccine that can be added during later childhood catch-up.
High risk means additive protection
Routine vaccines remain necessary before risk-specific pneumococcal, meningococcal, influenza or hepatitis doses are layered onto the plan.
Vaccination does not abolish fever risk
Asplenia and complement blockade still permit rapidly invasive infection, so the emergency fever pathway remains essential.
Households are part of protection
Completing safe vaccines in close contacts reduces the vulnerable child's chance of encountering measles, varicella or influenza.
Common pitfalls
01
Do not restart a valid primary course because the interval became longer than recommended.
02
Do not accept an assumed national schedule as proof that an individual overseas dose was given.
03
Do not use routine serology as a substitute for a structured catch-up plan.
04
Do not space compatible vaccines into extra visits without a product-specific reason.
05
Do not give late rotavirus after the upper age limit.
06
Do not give a live vaccine during severe immunosuppression without explicit specialist clearance.
07
Do not apply the routine PCV13 schedule to a child who meets the current high-risk PCV20 pathway.
08
Do not imply that MenB, MenACWY or pneumococcal vaccination eliminates infection risk in asplenia or complement inhibition.
09
Routine and additional vaccines for clinical risk groups in the current programme.
count towards the routine two-dose course; leave at least 4 weeks between valid post-birthday doses.
Asplenia or splenic dysfunction requires additional meningococcal, pneumococcal and annual influenza protection, but vaccination never replaces fever action plans and antimicrobial prophylaxis where prescribed.
Complement deficiency or complement-inhibitor treatment requires MenACWY and MenB and risk-specific pneumococcal and influenza vaccination; invasive meningococcal risk persists after vaccination.
Severe immunosuppression usually contraindicates live vaccines, reduces responses to inactivated vaccines and requires specialist timing around chemotherapy, biologics or transplant.
Vaccinate household contacts fully to create indirect protection; most live vaccines are safe for healthy contacts, with specific precautions for very severely immunosuppressed people.
Use the current Green Book disease chapter for exact product, dose number, interval and revaccination plan because high-risk pneumococcal and immune schedules change.
A significant measles or varicella exposure in an immunocompromised child is time critical and needs same-day specialist and health-protection advice.
Children starting complement-inhibitor therapy require MenACWY and MenB planning ideally at least 2 weeks beforehand, with antibiotic protection when the treatment cannot wait.
Planned splenectomy or immunosuppressive treatment should trigger vaccination review early; delaying review until after the procedure can reduce response or restrict live-vaccine options.
A child arriving with no reliable record must not be assumed protected because a country normally offers a vaccine or because a parent recognises a vaccine name.
Rotavirus has strict upper age limits; attempting to complete it outside the licensed programme window creates avoidable risk rather than useful catch-up.
05Pneumococcal risk classification
Why
Select routine PCV13 versus risk-specific PCV20 timing and later doses.
Interpretation and limitations
Distinguish severe immunocompromise, asplenia and complement disorder from other clinical risks and use the current 2026 pneumococcal schedule and local stock transition.
06Exposure risk assessment
Why
Identify time-critical need for post-exposure vaccine, immunoglobulin, antiviral or antibiotic action.
Interpretation and limitations
Confirm index diagnosis, closeness and timing, immune status and valid vaccination history, then use health-protection and disease-specific guidance.
2
Retain valid doses despite a long delay, give all compatible missing products today and choose formulations that complete each antigen efficiently.
3Schedule remaining doses and boosters at current minimum intervals and assign named recall responsibility across GP, school and specialist services.
03High-risk diagnosisAdd condition-specific protectionAsplenia, complement disorder, severe immunocompromise or another Green Book clinical risk is identified.+
1Complete the routine schedule and retrieve the current disease-specific Green Book tables for pneumococcal, meningococcal, influenza and any condition-specific vaccine.
2Coordinate timing with the responsible specialist, ideally vaccinating at least 2 weeks before elective splenectomy, complement inhibition or immunosuppressive treatment when clinically possible.
3Document residual infection risk, fever or exposure action, antimicrobial prophylaxis where prescribed and the future booster or revaccination schedule.
04Live vaccine decisionConfirm immune safety before dosingMMR, MMRV, varicella, rotavirus, BCG, LAIV or another live vaccine is due and immune status may be impaired.+
1Identify the precise disease, treatment, dose and last administration, planned next treatment and any transplant or immune-reconstitution milestones.
2Seek explicit advice from the responsible immunology, oncology, transplant or infection team and apply the current Green Book treatment-specific interval.
3If contraindicated, give indicated inactivated vaccines, use an inactivated influenza product, vaccinate eligible household contacts and create an exposure-prophylaxis plan.
Exact number and interval depend on age, previous PCV13, PCV20, PPV23, MenB and MenACWY, risk group and 2026 stock transition. Vaccination is incomplete protection and never replaces urgent fever assessment.
Reduces influenza and secondary decompensation in children with chronic or immune conditions.
Annual influenza vaccine
Give every influenza season from 6 months of age when the child is in a clinical risk group, using the season's age-appropriate inactivated product under 2 years or when LAIV is contraindicated, and LAIV when eligible and suitable.
Check the current annual programme, previous seasonal doses, severe immunosuppression, salicylate treatment and household exposure to a person in protective isolation before selecting LAIV.
Do not
omit household-contact vaccination, exposure advice, recall ownership or a written next-dose date.