There is a pus-filled lump on the newborn's left arm where the vaccination was given.

It is possible for a newborn to develop an abscess on the left arm after a vaccination due to normal reactions, improper injection technique, decreased immunity, allergic reactions, or local infection. Treatment should be based on the specific cause.

1. Normal phenomenon

Generally, newborns are required to receive hepatitis B and BCG vaccines after birth. Typically, following administration of the BCG vaccine, an abscess may appear at the injection site on the arm. This is usually a normal reaction to vaccination and does not require special treatment. As the abscess gradually breaks down and heals, a scar will form locally, which indicates successful BCG vaccination.

2. Improper injection

This may occur if healthcare personnel use incorrect injection techniques, such as injecting the medication into the skin rather than the subcutaneous tissue, leading to abscess formation. The area can be disinfected with iodophor, which may help promote resolution of the abscess.

3. Decreased immunity

If the newborn's immune system is weakened or the baby is physically frail, the injection site may become more susceptible to irritation, increasing the likelihood of abscess formation. Immunity can be improved through appropriate care and enhanced nutrition.

4. Allergic reaction

The abscess may result from an allergy to components in the vaccine, causing skin allergic reactions accompanied by symptoms such as itching and rashes. Antiallergic medications such as loratadine granules, desloratadine syrup, or cetirizine hydrochloride syrup may be used under medical guidance.

5. Local infection

Infection may occur if water enters the injection site or if clothing causes friction, allowing bacteria to infect the area and cause redness, swelling, and abscess formation. Under a doctor’s supervision, topical antibiotics such as erythromycin ointment, mupirocin ointment, or fusidic acid cream may be applied to treat the infection.

After vaccination, it is recommended to keep the injection site clean and dry, avoiding contact with water too soon to prevent infection. If symptoms are severe, prompt medical attention should be sought for appropriate evaluation and treatment under professional guidance.