Since the introduction of PCV7 for children important changes in IPD have occurred in many countries. People over 65 are at increased risk for developing IPD, mainly because of the ageing process and associated co-morbidities. For these reasons pneumococcal immunization has been recommended in this group of patients 
. Prior to 2011 only the 23-valent pneumococcal polysaccharide vaccine was available for adult immunization, but recently the pediatric conjugate vaccine with an enhanced immunological response, PCV13, has been approved for adult vaccination in Europe and the US. Knowledge of the current serotype distribution of pneumococci causing IPD in adults over 65 would therefore be helpful in order to establish the current coverage of this new vaccine in this age group.
In this way, three European regions recently replaced PCV7 for PCV13 (Germany in December 2009, England and Wales in April 2010 and the Autonomous Region of Madrid in June 2010) in routine childhood vaccination. In these regions an early effect of reduction of IPD has been observed in children under 2 years (target population). Moreover a reduction of IPD due to serotypes 19A and 7F has been demonstrated in England and Wales. These preliminary data support the beneficial effect that could be achieved after PCV13 vaccination of adults. 
In Spain the PCV7 vaccine for children was introduced in 2001 but it was not subsidized by the government, with exception of the Autonomous Region of Madrid which started universal childhood vaccination in November 2006 (more than 95% of children vaccinated). Currently, in this Spanish region PCV7 serotypes accounted for less than 5% of pediatric IPD episodes 
. However, in the rest of the country, the use of PCV7 did increase on a voluntary basis through the private sector, and childhood vaccination rates (excluding the Madrid Region) are estimated to be around 50–60% 
. In agreement with other studies carried out in countries where PCV7 has been used, we observed a marked decrease in PCV7 serotypes among pneumococci causing IPD in older adults due to herd protection 
. Overall, a major benefit of decreasing PCV7 serotypes was the fall in antibiotic resistance. However, other non-PCV7 serotypes increased, mainly due to clonal expansion 
. For instance, the rise in serotypes 1 and 7F in the 2007–2009 period was associated with the clonal expansion of Sweden1
-ST306 and Netherlands7F
-ST191, respectively, as observed during the first decade of this century in most European countries 
. However, the most notorious was the dramatic increase in serotype 19A, as observed in many countries after PCV7 introduction, especially in children under 5 years of age 
. In our study, serotype 19A is currently the first cause of invasive disease in older adults, as reported recently in France; furthermore, and as described previously, serotype 19A pneumococci were multiclonal 
. The important role acquired by serotype 19A makes it necessary to include this serotype in the routine vaccination of older adults. Moreover, multidrug resistance, which is frequent in this serotype, is related to two clones: CC230 and CC320. CC320 is the major contributor to the increase in resistant serotype 19A pneumococci in the US and in Asia, but only 3 isolates from the present study belonged to this CC 
. Here, as in most other studies from other European countries, the multidrug resistant strains are mainly associated with ST276 or ST2013, which are single locus and double locus variants of Denmark14
. In fact, CC230, which also includes isolates of serotype 24F with ST230, ranks first among invasive isolates in the present study.
In 2010, PCV13 replaced PCV7 for child vaccination, and PCV13 has recently been approved for adults. Given the results obtained after PCV7 introduction one would expect to see a progressive decrease in PCV13 serotypes among older adults over the next few years. In fact, in the UK when the universal PCV13 vaccination started in April 2010 a decrease in PCV13 serotypes (mainly 7F and 19A) has been observed in children and also in adults by herd protection 
. In this scenario, however, it is important to know which serotypes could be prone to increase in the near future. Our results showed an increase in serotype 24F (non-PCV13) associated with the expansion of the ST230 clone, which was described in Italy as a cause of meningitis 
. However, this serotype-genotype association (24F-ST230) was only detected in Catalonia. As regards serotype 6C, which emerged in the 2007–2009 period accounting for 2.1% of invasive isolates, the increase was multiclonal. Although serotype 6C is not included in the current PCV13, cross-protection between serotypes 6A and 6C has been reported 
. Surveillance studies are therefore needed in order to determine the impact of PCV13 on serotype 6C trends. The increases observed in other non-PCV13 serotypes such as 22F, 12F, 16F and 35B may suggest that these serotypes could play an important role in adult IPD in the near future. In fact, serotypes 22F, 12F and 16F had low genetic diversity thus the observed increase was due to a clonal expansion (ST433, ST989, and CC30, respectively). Then, a surveillance of these serotypes and genotypes should be performed to know the impact of PCV13 introduction.
Regarding clinical manifestations we observed no important changes, with pneumonia being the most common cause of IPD in people over 65 and accounting for 80% of IPD episodes. Contrary to what has been observed in children in our country, we found no increase in empyema in these patients, probably because serotype 1 is less frequent in older adults than it is in children 
. The burden of IPD in older adults is an increasing problem in many parts of the world, mainly due to the associated co-morbidities and the increased life expectancy. In our study we observed no significant changes in co-morbidities, with the exception of cancer, which probably reflects the increased rate of cancer diagnoses among the elderly.
The impact of child PCV7 vaccination on IPD in older adults (herd protection) that has been demonstrated in the present study, as well as by others, reinforces the relevance of adult vaccination with conjugate vaccines 
. In Europe, PCV10 and PCV13 are currently used for children, and the latter has recently been approved for adults over 50. Although we have not addressed this study to adults 50–65, 64.7% of IPD occurred in people over 50 in 2007–2009 period in the three hospitals of the present study were caused by serotypes included in PCV13. In the current scenario, and given the efficacy of PCV7, the preliminary data of PCV13 vaccination, and the coverage of PCV13 for adults over 65 (59.3%) or over 50 (64.7%), PCV13 could be a good vaccination option for the elderly in Spain. However, this study is focused on two Spanish regions and some regional differences have been observed, therefore it is necessary to have local data in order to establish the PCV13 coverage in each region. Finally, further studies will be needed in order to evaluate the effects of PCV13 introduction.