A study found that California law restricting non-medical exemptions is effective at increasing measles vaccination rates. Photo by Tumisu/Pixabay.
Dec. 23 (UPI) -- Laws aimed at parents who refuse to vaccinate their children against measles -- for religious or other reasons -- have been effective at increasing the numbers of kids who ultimately get the protective shot, a new study has found.
In an article published Monday in the journal PLOS Medicine, researchers reported that a California law passed in 2016 that eliminated non-medial exemptions for receiving the preventative vaccine "worked as intended" by increasing childhood vaccination rates in the state by an average of more than 4 percent.
Still, the authors also documented a small uptick in the number of medical exemptions sought for by parents in the state since the law's implementation.
"Vaccine hesitancy and the recent decline in vaccination rates is an increasing threat to public health," study co-author Dr. Nathan C. Lo, a medical resident at the University of California-San Francisco, said in a statement. "Our study shows that government policy has a role to address this, and that eliminating non-medical exemptions is an effective way of increasing vaccination coverage."
The United States has experienced several measles outbreaks in 2019. According to the Centers for Disease Control and Prevention, nearly 1,300 confirmed cases of the disease nationwide have been reported so far this year, up from fewer than 400 in 2018.
Many of the outbreaks have been linked with foreign travel. However, the disease has been allowed to spread in communities in which vaccination rates are low.
Although a vaccine against the virus has been available since the early 1970s, and the CDC has strongly recommended the two-dose shot for the vast majority of children, rates of its use have declined slightly across the country in recent years. In some cases, parents have refused the shots for their children for religious reasons.
However, the decline in vaccine "uptake" also has been linked with erroneous reports that the shot causes autism in children.
For their study, Lo and colleagues estimated how many California children would have received the measles, mumps and rubella, or MMR, vaccine if the law had not gone into effect and compared that to how many children were vaccinated following the law's enactment in 2016. The comparison group was created "synthetically" using data from 44 other states that do not have similar laws.
They then compared overall vaccine coverage in California counties from 2010 through 2017 to vaccine coverage in similar counties from 16 other states.
The analysis showed that MMR vaccination rates across the state increased 3.3 percent, compared to the "synthetic" state control, while non-medical exemptions decreased by 2.4 percent. Medical exemptions increased 0.4 percent.
At the county level, overall vaccination coverage went up on average by 4.3 percent, while non-medical exemptions dropped 3.9 percent and medical exemptions went up 2.4 percent. In some counties, the authors noted, vaccination rates jumped by as much as 26 percent, with the largest increases in counties that had the lowest vaccine coverage before the law took effect.
"We did see an increase in medical exemptions, but in absolute terms the numbers remain small -- 1 to 2 percent, driven largely by a few counties -- and we can expect them to remain of similar magnitude in the near term," Lo said. "Overall vaccine coverage increased by 10 to 20 percent in the high-risk counties, far more than the increase in medical exemptions."
According to the authors, the findings provide definitive evidence of the effectiveness of the California law, as policymakers across the United States and around the world debate similar requirements.
The new law helped restore "herd immunity" to measles in the Golden State by bringing its vaccination rate to 95 percent, which is sufficient to prevent outbreaks and prevent disease spread older children who cannot receive vaccinations for various medical reasons, they noted.