Infectious Disease and Vaccine Update: Dr. Ray O'Connor's Insights

Dr Ray O’Connor takes a look at recent clinical articles on the importance of promoting vaccines for Measles, HIV, Gonorrhoea, and other debilitating and deadly diseases In many ways vaccination has become a victim of its own success in that many healthcare professionals do not remember how severe the underlying diseases can be. I wish to look at some recent papers reminding us of the need to be vigilant and to keep promoting vaccination. Invasive pneumococcal disease Invasive pneumococcal disease (IPD) is a severe systemic infection caused by Streptococcus pneumoniae, presenting as pneumonia, meningitis, sepsis, and bacteraemia. To protect against pneumococcal disease, several countries, including Ireland, offer the 23-valent pneumococcal polysaccharide vaccine (PPV23) or pneumococcal conjugate vaccines (PCV13, PCV15, or PCV20) to older adults and individuals with underlying comorbidities. PPV23 is currently recommended for adults aged 65 years or older. IPD is associated with increased long-term mortality, but it is unclear if this is explained by pre-existing comorbidities. The aim of this matched cohort study1 was to compare long-term survival (>120 days after infection) in individuals with IPD and comparators without IPD. Cases were individuals aged 65 years or older with laboratory-confirmed IPD. Comparators matched on age, sex, and calendar date of laboratory-confirmed diagnosis were drawn from primary care electronic health records. The authors included 13,401 IPD cases and 67,005 comparators without IPD. There were 5,038 (53⋅5 per cent) female and 4,380 (46⋅5 per cent) male IPD cases and 19,927 (53⋅5 per cent) female and 17,351 (46⋅5 per cent) male comparators without IPD. After adjusting for comorbidities, socio-economic deprivation and ethnicity, the authors found increased all-cause mortality in IPD cases compared with comparators without IPD (hazard ratio 3⋅74). The predicted median survival was 4⋅7 years for IPD cases and more than 11⋅9 years for comparators without IPD. This increased mortality was consistent across subgroups defined by age, vaccination history, and comorbidity status. IPD was associated with increased mortality at least five years after infection. These findings emphasise the value of IPD prevention, (including vaccination) and the need for more research into the clinical management of people who have had IPD. Human Papilloma Virus Vaccination Human papillomavirus (HPV) vaccination has substantially reduced the incidence of high-grade cervical lesions (HSIL+) among vaccinated individuals. However, indirect effects on unvaccinated populations remain unclear. The authors of this nationwide, retrospective, register-based cohort study2 assessed herd effects by examining age-varying HSIL+ incidence among unvaccinated women in Sweden. The study looked at girls and women born between 1985 and 2000, using data from the Swedish National Cervical Screening Registry and several national health and population registries. Participants were grouped by birth cohorts exposed to different HPV vaccination strategies: opportunistic vaccination (1985–88; reference group), subsidised vaccination (1989–92), catch-up vaccination (1993–98), and school-based vaccination (1999–2000). Participants were followed up from age 10 years or from Jan 1, 2006, whichever came later, until their first HPV dose, an HSIL+ diagnosis, emigration, death, their 35th birthday, or Dec 31, 2022. Of 857,168 girls and women who had not been previously vaccinated for HPV or received a diagnosis of HSIL+ at baseline, the authors identified 42,274 cases of HSIL+, with cumulative incidence differing across birth cohorts and lowest in the 1999–2000 cohort. The findings were that HSIL+ incidence in unvaccinated women declined in the birth cohort eligible for HPV vaccination through a school-based programme. The conclusion is that the herd effect can be achieved through high-coverage HPV vaccination. Varicella The varicella vaccine is now included in Ireland’s childhood vaccination schedule for children born on or after October 1, 2024. Those children will be offered the first dose at 12 months of age and a second dose later (as part of the school-age vaccine programme). There may be some reluctance on the part of parents to accept the vaccine. There is an excellent information piece published in the BMJ3 which should address most of the questions that a parent might have about the vaccine. Although it is written for the UK, the points are also relevant for Ireland. The overall opinion is in favour of vaccination. Measles Measles is a highly contagious virus with a primary case reproduction number (i.e., the average number of secondary cases per case patient) of 12 to 18. It is currently spreading rapidly owing to reduced measles vaccination coverage, which is due primarily to the disruption of local immunization programs by the Coronavirus Disease 2019 (COVID-19) pandemic and of growing vaccine hesitancy. Since 2024, all World Health Organization (WHO) regions have reported increased numbers of measles cases, with 395,521 laboratory confirmed measles cases reported in 2024. It is timely then that a very comprehensive paper on the disease has been recently published.4 This has some really useful information on the high levels of morbidity, mortality and infectivity of the disease in unvaccinated people. The authors also make the point that waning levels of maternal measles antibodies at three to four months of age has increased measles risk in young infants. Further research on the effectiveness of early measles vaccination is needed. A sobering read! Gonorrhoea A world first gonorrhoea vaccine5 was rolled out from August 2025 in England with the aim of reducing soaring cases. The programme involved local authority commissioned sexual health clinics to offer the 4CMenB vaccine to patients at highest risk of the sexually transmitted infection (STI). This includes including gay and bisexual men with a recent history of multiple sexual partners or a bacterial STI in the previous 12 months. It is claimed that the vaccine offers 30-40 per cent protection from the infection, and the Department of Health and Social Care hopes that it could prevent as many as 100,000 cases. Drug resistant strains of Neisseria gonorrhoeae are spreading in many countries, making antibiotics—including the most used treatments, ceftriaxone and cefixime—ineffective against infection. In a potential turning of the tide, two new antibiotics were approved for gonorrhoea in the US by its Food and Drug Administration (FDA) in December 2025: gepotidacin (marketed as Blujepa) and zoliflodacin (brand name Nuzolvence).6 Both are still awaiting approval as gonorrhoea treatments in the UK and EU. Unlike existing antibiotics that kill bacteria by inhibiting synthesis of their cell walls, both gepotidacin and zoliflodacin inhibit bacterial DNA replication. They offer some hope for this very difficult to treat infection. HIV Finally, there are reports of a new highly effective drug to combat Human Immunodeficiency Virus (HIV).7 Lenacapavir is a long acting, injectable, pre-exposure prophylaxis (PrEP) drug that prevents HIV infection. The drug is an HIV-1 capsid inhibitor, meaning that it disrupts the protein shell that protects the virus’s genetic material and enzymes so it cannot replicate. The drug can inhibit the virus at multiple stages in the life cycle, and has little to no cross resistance with existing antiretroviral agents. The early results of a phase 3 trial showed 100% protection against HIV infection among women, and its anticipated rollout would, it was hoped, be a game changer. After a period of considerable uncertainty following foreign aid cuts from the US government and others, news emerged that lenacapavir would be funded by the US President’s Emergency Plan for AIDS Relief. References: