"Disruption to immunisation programmes from the Covid-19 pandemic threatens to unwind decades of progress against vaccine-preventable diseases like measles," said WHO Director General Dr Tedros Adhanom Ghebreyesus.
The reasons for disrupted services vary. Some parents are reluctant to leave home because of restrictions on movement, lack of information or because they fear infection with the Covid-19 virus.
Other than that, many health workers are also unavailable because of restrictions on travel, or redeployment to Covid response duties, as well as a lack of protective equipment.
Many countries have temporarily and justifiably suspended preventive mass vaccination campaigns against diseases like cholera, measles, meningitis, polio, tetanus, typhoid and yellow fever, due to risk of transmission and the need to maintain physical distancing during the early stages of the Covid-19 pandemic.
Measles and polio vaccination campaigns, in particular, have been badly hit, with measles campaigns suspended in 27 countries and polio campaigns put on hold in 38 countries.
At least 24 million people in 21 Gavi-supported lower-income countries are at risk of missing out on vaccines against polio, measles, typhoid, yellow fever, cholera, rotavirus, HPV, meningitis and rubella due to postponed campaigns and introductions of new vaccines.
Gavi CEO Dr. Seth Berkley said: "Due to Covid-19 this immense progress is now under threat, risking the resurgence of diseases like measles and polio. Not only will maintaining immunisation programmes prevent more outbreaks, it will also ensure we have the infrastructure we need to roll out an eventual Covid-19 vaccine on a global scale."
Transport delays of vaccines are exacerbating the situation. UNICEF has reported a substantial delay in planned vaccine deliveries due to the lockdown measures and the ensuing decline in commercial flights and limited availability of charters.
To help mitigate this, UNICEF is appealing to governments, the private sector, the airline industry, and others, to free up freight space at an affordable cost for these life-saving vaccines.
"We cannot let our fight against one disease come at the expense of long-term progress in our fight against other diseases," said Henrietta Fore, UNICEF Executive Director.
Fore further said that while circumstances may require us to temporarily pause some immunisation efforts, immunisations must restart as soon as possible, or we risk exchanging one deadly outbreak for another.
Despite the challenges, several countries are making special efforts to continue immunization. Uganda is ensuring that immunisation services continue along with other essential health services, even funding transportation to ensure outreach activities.
In Laos, despite a national lockdown imposed in March, routine immunisation in fixed sites continued with physical distancing measures in place.