By Jeremy Laurance
London - Babies in Britain may not be receiving full protection against the deadly diseases of childhood because of the practice of giving vaccines in combination rather than singly.
Concern about the childhood vaccination programme was raised after researchers found that a combined vaccine against pneumococcal disease and meningitis C was less effective than individual jabs given singly.
The researchers from the Oxford Vaccines Group at Oxford University, say the findings do not have implications for the combined MMR vaccine against measles, mumps and rubella, but do raise questions about other vaccines, including whooping cough and Hib meningitis.
All children are offered at least seven vaccines in nine separate jabs before school age, and more vaccines against other diseases are being developed.
As the vaccination schedule becomes more crowded there is increasing pressure to combine vaccines to reduce the number of jabs.
Now doctors are warning that there may be unanticipated consequences of combining vaccines. Researchers in Oxford and Gloucester tested 240 infants, half of whom were given a new combination jab against pneumococcal disease and meningitis C, and half were given the single meningitis C vaccine.
Pneumococcal disease can cause meningitis, pneumonia and septicaemia but there is currently no vaccine against it included in the British vaccination schedule. In the US there was a 69 percent reduction in the incidence of pneumococcal disease within two years of the vaccine's introduction.
Meningitis C vaccine given as a single jab was introduced in Britain in 1999 and has reduced the incidence of the disease by 87 percent. But it is not offered in the US.
The results of the study showed that those given the jab combining the two vaccines had lower immunity against meningitis C than those who received the single jab. The authors say in the Journal of the American Medical Association (Jama): "These results highlight the unpredictability of the immune responses ... after incorporating multiple antigens into combination vaccines."
Alarm about the consequences of combining jabs was raised in the UK in 2003, when there was a fivefold increase in cases of meningitis caused by haemophilus influenzae B (Hib). The number of affected children rose from 20 to 100, half of whom were under five.
All the children had been vaccinated against Hib and were classed as "vaccine failures" and the Government ordered a one-off Hib booster jab to be given to all children up to the age of four in 2003.
The failure has been attributed to an interaction with the whooping cough vaccine with which the HiB vaccine was combined. Children given an acellular type of whooping cough vaccine - one of several types used in the combination - were found to be eight times more likely to be vaccine failures than those given other types.
Anthony Harnden, a lecturer in general practice at Oxford University and an author of the Jama study, said: "These combination vaccines are potentially a problem. It seems to be completely unpredictable which combinations cause reductions in immunity. The only way to find out is to do a trial."
Jim Buttery, who led the study and is now at the University of Melbourne, Australia, said the findings had no relevance to the debate over MMR vaccine.
Campaigners have called for the combined MMR vaccine to be split and given as three separate jabs because of unproved allegations that the combination may cause bowel disease and autism.
"MMR vaccine has been checked to make sure each component is immunogenic including the form used in the UK. I do not believe this study has any bearing on MMR," he said.
Needles: a fact of childhood life
Babies have to get used to being jabbed with needles from an early age. Their first jab is a combination of vaccines against diphtheria, tetanus, whooping cough and Hib meningitis.
Polio vaccine, previously given orally as drops on a sugar lump, is also now included in this combined injection. The change was made after the incidence of polio fell so low that the risk to elderly people, who had never been vaccinated, from the vaccine excreted by babies was greater than that to the babies themselves.
The combined jab, containing five vaccines, is given at two, three and four months of age. At the same time, three doses of the single meningitis C vaccine are given in a single jab.
If the proposed pneumococcal vaccine cannot be combined with the meningitis C jab then babies will face three injections at each clinic visit instead of the current two.
After 12 months, infants receive their first MMR jab. Around age four, they receive a pre-school MMR booster and a separate booster of diphtheria, tetanus, whooping cough Hib meningitis and polio.
Between 10 and 14 they are tested with BCG for tuberculosis and, if needed, given one injection against the disease. Between 13 and 18 they are given a booster of diphtheria, tetanus and polio.
Further vaccines are being researched for possible addition to the immunisation schedule. These include those against pneumococcal disease, which is used in the US, chickenpox and rotavirus, which causes childhood diarrhoea.