Since their son Fletcher was born nine months ago, Sarah Chivers and her husband, Andrew, have chosen not to have him vaccinated against childhood diseases.
The Scarborough couple are among an increasing number of parents who believe potential exposure to serious diseases such as whooping cough and hepatitis B is preferable to the potential side effects of vaccines.
Ms Chivers said Fletcher was thriving and they did not regret their choice.
"We talked about it quite extensively and I did quite a bit of research," she said. "When he was born, we decided not to do it."
Ms Chivers said she and her husband were concerned about the detrimental effects of vaccines.
"The consequences of being vaccinated with side effects and something going wrong are greater than the risk of him catching something and allowing his immune system to fight it naturally," she said.
By his age, Fletcher would have had jabs for hepatitis B, diphtheria, tetanus, whooping cough, polio, Hib, pneumococcal disease and rotavirus under the national immunisation program. Instead, Fletcher is vaccine-free and Ms Chivers said he has only ever had one cold. As the only one in her 14-strong mothers' group who does not vaccinate her child, Ms Chivers said her choice generated questions and interest.
"I'm not really one for going around advising," she said. "It's up to every individual parent to decide."
She said some of the children in the group had had strong reactions to vaccinations.
Ms Chivers said she still breastfed Fletcher to give him extra antibodies.